Elasticity tensor and ultrasonic velocities for anisotropic cubic polycrystal
Institute of Scientific and Technical Information of China (English)
2008-01-01
The orientation distribution of crystallites in a polycrystal can be described by the orientation distribution function(ODF) . The ODF can be expanded under the Wigner D-bases. The expanded coefficients in the ODF are called the texture coefficients. In this paper,we use the Clebsch-Gordan expression to derive an explicit expression of the elasticity tensor for an anisotropic cubic polycrystal. The elasticity tensor contains three material constants and nine texture coefficients. In order to measure the nine texture coefficients by ultrasonic wave,we give relations between the nine texture coefficients and ultrasonic propagation velocities. We also give a numerical example to check the relations.
Whitney, Donna; Seaton, Nca
2010-05-01
Electron backscattered diffraction (EBSD) studies have revealed complex microstructures in garnet, including features developed during crystal growth and/or deformation. New data show that garnets commonly grow as clusters of grains (polycrystals) juxtaposed by high-angle boundaries. Garnet polycrystals may form at any stage of metamorphism following nucleation of garnet: polycrystals may form early as a result of close spacing of nuclei, or later via impingement of larger grains. EBSD analysis of garnets in metamorphic rocks from 9 localities in the US, Canada, Turkey, Iran, and Colombia detected polycrystals at every site. Evidence for internal deformation of garnet was observed in only one sample, a calc-pelite dominated by plagioclase; all other samples are mica schists. Three sites displayed garnet shape-preferred orientation, but none had a crystallographic preferred orientation of garnet. In some samples, polycrystals comprise ~20-30% of garnets analyzed. Some early-coalescing polycrystals exhibit growth zoning concentric about the geometric center of the polycrystal; i.e., zoning is unrelated to the location of internal grain boundaries. In other polycrystals, Fe-Mn-Mg zoning has a different pattern than that of Ca. Some polycrystals are characterized by high-angle misorientation boundaries in special orientations, indicating that these polycrystals are not random clusters of grains. Special boundaries were detected in 0-60% of garnets analyzed. Polycrystal formation may relate to the presence of chemical or textural heterogeneities (e.g. precursor phases, deformation features) that allowed close spacing of garnet nuclei. It is important to recognize polycrystals because internal grain boundaries may affect diffusion pathways and length scales and may facilitate communication of garnet interiors with matrix phases, thereby influencing reaction history and garnet composition and zoning.
Geometry of polycrystals and microstructure
Directory of Open Access Journals (Sweden)
Ball John M.
2015-01-01
Full Text Available We investigate the geometry of polycrystals, showing that for polycrystals formed of convex grains the interior grains are polyhedral, while for polycrystals with general grain geometry the set of triple points is small. Then we investigate possible martensitic morphologies resulting from intergrain contact. For cubic-totetragonal transformations we show that homogeneous zero-energy microstructures matching a pure dilatation on a grain boundary necessarily involve more than four deformation gradients. We discuss the relevance of this result for observations of microstructures involving second and third-order laminates in various materials. Finally we consider the more specialized situation of bicrystals formed from materials having two martensitic energy wells (such as for orthorhombic to monoclinic transformations, but without any restrictions on the possible microstructure, showing how a generalization of the Hadamard jump condition can be applied at the intergrain boundary to show that a pure phase in either grain is impossible at minimum energy.
Dilational Response of Voided Polycrystals
Savage, Daniel J.; Cazacu, Oana; Knezevic, Marko
2017-02-01
Finite-element (FE) cell model computations have been used to gain insights into the ductile response of porous polycrystals. Generally, the behavior of the matrix is described by a J 2-plasticity model. In this article, we present a new computational approach to FE cell models for porous polycrystals deforming by slip based on crystal plasticity. The cell provides the homogenized dilational response, where the constitutive response of every integration point is based on a single-crystal visco-plasticity law. The calculations are performed for a body-centered cubic polycrystal with random texture. Axisymmetric tensile and compressive loadings are imposed corresponding to the fixed values of the stress triaxiality and to two possible values of the Lode parameter. The resulting numerical yield points are compared with those obtained using a J 2-FE cell and an analytical model. The predictions confirm the combined effects of the mean stress and third-invariant on yielding recently revealed by the analytical model.
pH-responsive lyotropic liquid crystals for the preparation of pure cubic zirconia nanoparticles
He, Wei Yan; Liu, Jin Rong; He, Zhang; Cao, Zhen Zhu; Li, Cai Hong; Gao, Yan Fang
2016-07-01
We present a lyotropic liquid crystal system consisting of SDS/Triton X-100/water at 25 °C. This system is respond to pH variations with a phase switch. When pH is altered from alkaline (pH 13) to acidic (pH 2) conditions, phase change occurs from a bicontinuous hexagonal phase to a partially hexagonal phase until it disappears. The hexagonal phase under alkaline conditions is stable. Thus, this system is an ideal candidate for the preparation of pure cubic ZrO2 nanoparticles. XRD results confirm that the as-synthesized powder is composed of pure cubic ZrO2. These nanoparticles also exhibit a thermal stability of up to 800 °C. The size and morphological characteristics of the nanoparticles are greatly affected by ZrOCl2 concentration. The mechanism of zirconia nanoparticle synthesis in a lyotropic hexagonal phase was proposed.
pH-responsive lyotropic liquid crystals for the preparation of pure cubic zirconia nanoparticles
Energy Technology Data Exchange (ETDEWEB)
He, Wei Yan; Liu, Jin Rong; He, Zhang; Cao, Zhen Zhu; Li, Cai Hong; Gao, Yan Fang [Inner Mongolia University of Technology, School of Chemical Engineering, Hohhot (China)
2016-07-15
We present a lyotropic liquid crystal system consisting of SDS/Triton X-100/water at 25 C. This system is respond to pH variations with a phase switch. When pH is altered from alkaline (pH 13) to acidic (pH 2) conditions, phase change occurs from a bicontinuous hexagonal phase to a partially hexagonal phase until it disappears. The hexagonal phase under alkaline conditions is stable. Thus, this system is an ideal candidate for the preparation of pure cubic ZrO{sub 2} nanoparticles. XRD results confirm that the as-synthesized powder is composed of pure cubic ZrO{sub 2}. These nanoparticles also exhibit a thermal stability of up to 800 C. The size and morphological characteristics of the nanoparticles are greatly affected by ZrOCl{sub 2} concentration. The mechanism of zirconia nanoparticle synthesis in a lyotropic hexagonal phase was proposed. (orig.)
Constitutive relation of weakly anisotropic polycrystal with microstructure and initial stress
Institute of Scientific and Technical Information of China (English)
Mojia Huang; Hua Zhan; Xiuqiao Lin; Hai Tang
2007-01-01
Man (Nondestr Test Eval 15:191-214, 1999) derived the constitutive relation of a weakly-textured orthorhombic aggregate of cubic crystallites with effects of microstructure and initial stress. In this paper, a computational expression on the integration ∫SO(3)Qh× Dl m0 is given. Then, by means of the computational expression, the general constitutive relation of a weakly-textured anisotropic polycrystal with the consideration of microstructure and initial stress is derived. As special cases of our general constitutive relation, two constitutive relations are given for an isotropic polycrystal and a weakly-textured anisotropic aggregate of cubic crystallites. The acoustoelastic tensor of the reference cubic crystal is derived to determine the material constants of the polycrystal. Two examples are given for understanding the physical meaning of the texture coefficients and the constitutive relations.
Preparation of microcrystals in lipidic cubic phase for serial femtosecond crystallography.
Liu, Wei; Ishchenko, Andrii; Cherezov, Vadim
2014-09-01
We have recently established a procedure for serial femtosecond crystallography (SFX) in lipidic cubic phase (LCP) for protein structure determination at X-ray free-electron lasers (XFELs). LCP-SFX uses the gel-like LCP as a matrix for growth and delivery of membrane protein microcrystals for crystallographic data collection. LCP is a liquid-crystalline mesophase composed of lipids and water. It provides a membrane-mimicking environment that stabilizes membrane proteins and supports their crystallization. Here we describe detailed procedures for the preparation and characterization of microcrystals for LCP-SFX applications. The advantages of LCP-SFX over traditional crystallographic methods include the capability of collecting room-temperature high-resolution data with minimal effects of radiation damage from sub-10-μm crystals of membrane and soluble proteins that are difficult to crystallize, while eliminating the need for crystal harvesting and cryo-cooling. Compared with SFX methods for microcrystals in solution using liquid injectors, LCP-SFX reduces protein consumption by 2-3 orders of magnitude for data collection at currently available XFELs. The whole procedure typically takes 3-5 d, including the time required for the crystals to grow.
Zhang, Wei; Li, Xiaolin; Yang, Zhi; Tang, Xuehui; Ma, Yujie; Li, Ming; Hu, Nantao; Wei, Hao; Zhang, Yafei
2016-07-01
There has been a growing interest in gathering together photocatalysis of semiconductors, like cuprous oxide (Cu2O), and the excellent electron transmittability of graphene to produce a graphene-based semiconductor for photocatalytic degradation. In this paper, a mild one-pot in situ synthesis of cubic cuprous oxide-reduced graphene oxide (Cu2O-RGO) nanocomposites has been proposed for the removal of methyl orange. In contrast to pure cubic Cu2O particles under similar preparation conditions, the cubic Cu2O-RGO nanocomposites demonstrate enhanced visible-light-driven photocatalytic activity for methyl orange dye with a 100% degradation rate in 100 min. The enhanced photocatalytic performance is mainly attributed to the increased charge transportation, effective separation of photoelectrons from vacancies, and the improved contact area.
Modeling polycrystals with regular polyhedra
Directory of Open Access Journals (Sweden)
Paulo Rangel Rios
2006-06-01
Full Text Available Polycrystalline structure is of paramount importance to materials science and engineering. It provides an important example of a space-filling irregular network structure that also occurs in foams as well as in certain biological tissues. Therefore, seeking an accurate description of the characteristics of polycrystals is of fundamental importance. Recently, one of the authors (MEG published a paper in which a method was devised of representation of irregular networks by regular polyhedra with curved faces. In Glicksman's method a whole class of irregular polyhedra with a given number of faces, N, is represented by a single symmetrical polyhedron with N curved faces. This paper briefly describes the topological and metric properties of these special polyhedra. They are then applied to two important problems of irregular networks: the dimensionless energy 'cost' of irregular networks, and the derivation of a 3D analogue of the von Neumann-Mullins equation for the growth rate of grains in a polycrystal.
Ishchenko, Andrii; Cherezov, Vadim; Liu, Wei
2016-09-20
Membrane proteins (MPs) are essential components of cellular membranes and primary drug targets. Rational drug design relies on precise structural information, typically obtained by crystallography; however MPs are difficult to crystallize. Recent progress in MP structural determination has benefited greatly from the development of lipidic cubic phase (LCP) crystallization methods, which typically yield well-diffracting, but often small crystals that suffer from radiation damage during traditional crystallographic data collection at synchrotron sources. The development of new-generation X-ray free-electron laser (XFEL) sources that produce extremely bright femtosecond pulses has enabled room temperature data collection from microcrystals with no or negligible radiation damage. Our recent efforts in combining LCP technology with serial femtosecond crystallography (LCP-SFX) have resulted in high-resolution structures of several human G protein-coupled receptors, which represent a notoriously difficult target for structure determination. In the LCP-SFX technique, LCP is recruited as a matrix for both growth and delivery of MP microcrystals to the intersection of the injector stream with an XFEL beam for crystallographic data collection. It has been demonstrated that LCP-SFX can substantially improve the diffraction resolution when only sub-10 µm crystals are available, or when the use of smaller crystals at room temperature can overcome various problems associated with larger cryocooled crystals, such as accumulation of defects, high mosaicity and cryocooling artifacts. Future advancements in X-ray sources and detector technologies should make serial crystallography highly attractive and practicable for implementation not only at XFELs, but also at more accessible synchrotron beamlines. Here we present detailed visual protocols for the preparation, characterization and delivery of microcrystals in LCP for serial crystallography experiments. These protocols include
Rossetti, M.
1970-01-01
High purity molybdenum disilicide crystals are prepared by zone melting sintered compacts. This method yields single crystals or polycrystals free from macrocracks which allow better measurement and evaluation of mechanical properties.
Energy Technology Data Exchange (ETDEWEB)
Xu, Youguo; Liu, Yangai [School of Materials Science and Technology, China University of Geosciences (Beijing), Beijing 100083 (China); Huang, Zhaohui, E-mail: huang118@cugb.edu.cn [School of Materials Science and Technology, China University of Geosciences (Beijing), Beijing 100083 (China); Fang, Minghao [School of Materials Science and Technology, China University of Geosciences (Beijing), Beijing 100083 (China); Hu, Xiaozhi [School of Mechanical and Chemical Engineering, University of Western Australia, Perth, WA 6009 (Australia); Yin, Li; Huang, Juntong [School of Materials Science and Technology, China University of Geosciences (Beijing), Beijing 100083 (China)
2013-01-15
Graphical abstract: Display Omitted Highlights: ► Zircon carbothermal reduction was carried out in a tailor-made device at high-temperature air atmosphere. ► Fibre-like SiC and cubic-ZrO{sub 2}/SiC composite were obtained synchronically. ► Zirconium and silicon in zircon ore was initial separated. ► [SiO{sub 4}] was mutated to fibre-like SiC, while [ZrO{sub 8}] was transformed to cubic ZrO{sub 2}. ► The SiC were surprisingly enriched in the reducing atmosphere charred coal particles layers by gas–solid reaction. -- Abstract: Fibre-like SiC and cubic-ZrO{sub 2}/SiC composite were prepared respectively from zircon with yttrium oxide addition via carbothermal reduction process at 1600 °C for 4 h in an air atmosphere furnace, where the green samples were immerged in charred coal particles inside a high-temperature enclosed corundum crucible. The reaction products were characterized by XRD, XRF, XPS and SEM. The results indicate that ZrO{sub 2} in the products was mainly existed in the form of cubic phase. The reacted samples mainly contain cubic ZrO{sub 2}, β-SiC and trace amounts of zircon, with the SiC accounting for 14.8 wt%. Furthermore, a large quantity of fibre-like SiC was surprisingly found to concentrate in the charred coal particles layers around the samples. This study obtains fibre-like SiC and cubic-ZrO{sub 2}/SiC composite synchronically from zircon via carbothermal reduction process, which also bring a value-added high-performance application for natural zircon.
PREDICTION OF YIELD FUNCTIONS ON BCC POLYCRYSTALS
Institute of Scientific and Technical Information of China (English)
Huang Mojia; Fu Mingfu; Zheng Chaomei
2006-01-01
By the nonlinear optimization theory, we predict the yield function of single BCC crystals in Hill's criterion form. Then we give a formula on the macroscopic yield function of a BCC polycrystal Ω under Sachs' model, where the volume average of the yield functions of all BCC crystallites in Ω is taken as the macroscopic yield function of the BCC polycrystal. In constructing the formula, we try to find the relationship among the macroscopic yield function, the orientation distribution function (ODF), and the single BCC crystal's plasticity. An expression for the yield stress of a uniaxial tensile problem is derived under Taylor's model in order to compare the expression with that of the macroscopic yield function.
Mode-converted ultrasonic scattering in polycrystals with elongated grains.
Arguelles, Andrea P; Kube, Christopher M; Hu, Ping; Turner, Joseph A
2016-09-01
Elastic wave scattering is used to study polycrystalline media for a wide range of applications. Received signals, which include scattering from the randomly oriented grains comprising the polycrystal, contain information from which useful microstructural parameters may often be inferred. Recently, a mode-converted diffuse ultrasonic scattering model was developed for evaluating the scattered response of a transverse wave from an incident longitudinal wave in a polycrystalline medium containing equiaxed single-phase grains with cubic elastic symmetry. In this article, that theoretical mode-converted scattering model is modified to account for grain elongation within the sample. The model shows the dependence on scattering angle relative to the grain axis orientation. Experimental measurements were performed on a sample of 7475-T7351 aluminum using a pitch-catch transducer configuration. The results show that the mode-converted scattering can be used to determine the dimensions of the elongated grains. The average grain shape determined from the experimental measurements is compared with dimensions extracted from electron backscatter diffraction, an electron imaging technique. The results suggest that mode-converted diffuse ultrasonic scattering has the potential to quantify detailed information about grain microstructure.
Condensation of tetragonal zirconia polycrystals by reactive sputtering
Energy Technology Data Exchange (ETDEWEB)
Chen, I-M. [Institute of Materials Science and Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan (China); Yeh, S.-W. [Institute of Materials Science and Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan (China); Chiou, S.-Y. [Department of Mold and Die Engineering, National Kaohsiung University of Applied Science, Kaohsiung, Taiwan (China); Gan Dershin [Institute of Materials Science and Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan (China)]. E-mail: dgan@mail.nsysu.edu.tw; Shen Pouyan [Institute of Materials Science and Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan (China)
2005-11-22
Reactive sputtering on metallic Zr target under various oxygen flow rates was employed to produce nanocrystalline zirconia condensates, which were collected on a carbon-coated collodion film for analytical electron microscopic observations. With an Ar flow rate of 28 sccm, the collected condensates are cubic and tetragonal (t-) zirconia less than 10 nm in size under 0-2 sccm oxygen flow rate and increased to 10-20 nm in size with partial t- to monoclinic (m-) zirconia transformation at 3 sccm. Between 4 and 4.5 sccm, t-zirconia polycrystals (TZP) about 20 nm in grain size were formed by coalescence of the t-zirconia condensates. Above 6 sccm, the (111) and {l_brace}100{r_brace} specific coalescence as well as random attachment prevailed to form larger (> 30 nm) individual condensates of m-zirconia as the critical size of martensitic t-m transformation is exceeded. The TZP formation can be accounted for by the small grain size, the presence of low-valence Zr cation and the lateral constraint of neighboring grains.
Energy Technology Data Exchange (ETDEWEB)
Lebensohn, Ricardo A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Tomé, Carlos N. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Maudlin, Paul J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2003-08-01
In this work we consider the presence of ellipsoidal voids inside polycrystals submitted to large strain deformation. For this purpose, the originally incompressible viscoplastic self-consistent (VPSC) formulation of Lebensohn and Tomé (1993) has been extended to compressible polycrystals. In doing this, both the deviatoric and the spherical components of strain rate and stress are accounted for. Such an extended model allows us to account for the presence of voids and for porosity evolution, while preserving the anisotropy and crystallographic capabilities of the VPSC model. The formulation is adjusted to match Gurson model in the limit of rateindependent isotropic media and spherical voids. We present several applications of this extended VPSC model that address the coupling between texture, plastic anisotropy, void shape, triaxiality, and porosity evolution. This report contains a detailed and comprehensive derivation of the VPSC polycrystal model and of the equations associated with the theory. Such description is meant to serve as a general reference source for the VPSC formulation and is not limited to the particular case of voided polycrystals.
On the question of creep of anisotropic polycrystals
Directory of Open Access Journals (Sweden)
Simonyan A. M.
2012-03-01
Full Text Available On the base of dislocation slip conception the rheological behaviour of anisotropic polycrystals at complex stress state is considered. It is assumed that the anisotropy of polycrystals takes the place as a result of uneven distribution of slip system directions because of uneven distribution of single crystal grain orientations.
Energy Technology Data Exchange (ETDEWEB)
Martinet, C. [Laboratoire de Physico-Chimie des Materiaux Luminescents, CNRS-Universite Lyon1, 10, rue Andre-Marie Ampere, 69622 Villeurbanne Cedex (France)]. E-mail: martinet@pcml.univ-lyon1.fr; Pillonnet, A. [Laboratoire de Physico-Chimie des Materiaux Luminescents, CNRS-Universite Lyon1, 10, rue Andre-Marie Ampere, 69622 Villeurbanne Cedex (France); Lancok, J. [Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 18221 Prague (Czech Republic); Garapon, C. [Laboratoire de Physico-Chimie des Materiaux Luminescents, CNRS-Universite Lyon1, 10, rue Andre-Marie Ampere, 69622 Villeurbanne Cedex (France)
2007-10-15
Eu{sup 3+}-doped lutetium oxide (Eu:Lu{sub 2}O{sub 3}) nanocrystalline films were grown on fused-silica substrates by pulsed laser deposition. Depending on deposition conditions (oxygen pressure, temperature and laser energy), the structure of the films changed from amorphous to crystalline and the cubic or monoclinic phases were obtained with varying preferential orientation and crystallite size. The monoclinic phase could be prepared for the first time at temperatures as low as 240 deg. C and in a narrow range of parameters. Although this phase has been previously reported for powder samples, it occurs only for high pressures and high temperatures preparation conditions. The refractive indices were measured by m-lines spectroscopy for both crystalline phases and their dispersion curve fitted by the Sellmeier expression. The specific Eu{sup 3+} fluorescence properties of the different phases, monoclinic and cubic, were registered and show modifications due to the disorder induced by the nanometric size of the crystallites, emphasised in particular by quasi-selective excitation in the charge transfer band.
A Numerical Study of Localized Plastic Deformation in Polycrystals
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
A finite element formulation which derives constitutive responsefrom crystal plasticity theory was used to examine localized deformation in fcc polycrystals. The polycrystal model was an idealized planar array of 22 hexagonal grains. The constitutive description used is based on a finite strain kinematical theory that accounts for lattice rotations. Formation of shear bands was successfully modeled in both single crystal and polycrystals. Stress and strain distribution around triple junctions was also analyzed. Results show the distributions of stresses and strains are distinctly inhomogeneous. Stress and strain fields across grain boundaries are highly discontinuous.However, this discontinuity will be restrained when shear bands are fully developed.
Energy Technology Data Exchange (ETDEWEB)
Arief, Injamamul; Mukhopadhyay, P.K., E-mail: pkm@bose.res.in
2014-06-01
Cubic and spherical Fe{sub 55}Co{sub 45} alloyed microstructures were synthesized by borohydride reduction from aqueous solutions of metallic precursors, using stabilizers and polymer. Monosodium citrate, sodium acetate and PEG 6000 were utilized as electrostatic stabilizers and polymeric surface modifier. Suitable reaction conditions were maintained for synthesis of predominantly larger particles (0.7 µm to 1.2 µm), that facilitates use in magnetorheological fluids. Surface morphological studies by scanning electron microscopy revealed well shaped cubic and spherical geometry for the citrate and polymer-stabilized Fe{sub 55}Co{sub 45} alloys, while the alloy compositions remained nearly the same for both. X-ray diffractions of the as-prepared and annealed samples under various temperatures showed high degree of crystallinity with increasing temperatures. Studies of D.C. magnetization of the systems reveal that the particles have a core–shell structure, with inner magnetic core having a diameter around 30 nm with a log-normal distribution. Magnetorheological studies were performed with 8 vol% suspensions of as-synthesized particles dispersed in silicone oil (viscosity 30 mPa s at 25 °C) under different magnetic fields. Detailed studies of the magnetorheological properties were studied on these systems for practical use.
Directory of Open Access Journals (Sweden)
Kinjal Gandha
2017-05-01
Full Text Available Ferromagnetic Co-doped α-Fe2O3 cubic shaped nanocrystal assemblies (NAs with a high coercivity of 5.5 kOe have been synthesized via a magnetic field (2 kOe assisted hydrothermal process. The X-ray diffraction pattern and Raman spectra of α-Fe2O3 and Co-doped α-Fe2O3 NAs confirms the formation of single-phase α-Fe2O3 with a rhombohedral crystal structure. Electron microscopy analysis depict that the Co-doped α-Fe2O3 NAs synthesized under the influence of the magnetic field are consist of aggregated nanocrystals (∼30 nm and of average assembly size 2 μm. In contrast to the NAs synthesized with no magnetic field, the average NAs size and coercivity of the Co-doped α-Fe2O3 NAs prepared with magnetic field is increased by 1 μm and 1.4 kOe, respectively. The enhanced coercivity could be related to the well-known spin–orbit coupling strength of Co2+ cations and the redistribution of the cations. The size increment indicates that the small ferromagnetic nanocrystals assemble into cubic NAs with increased size in the magnetic field that also lead to the enhanced coercivity.
Garnet polycrystals and the significance of clustered crystallization
Whitney, Donna L.; Seaton, Nicholas C. A.
2010-10-01
Polycrystalline garnets are common in metamorphic rocks and may form as a result of close spacing of nuclei (if clustering is early) or impingement of larger grains (if clustering occurs later in the growth history). The timing of clustering relative to garnet growth is relevant to understanding the formation and evolution of porphyroblasts and evaluating the significance (if any) of clustering. Electron backscattered diffraction (EBSD) analysis of garnet-bearing metamorphic rocks reveals the presence of polycrystalline garnet in nine localities examined in this study: the northern Appalachians (Vermont, Maine, New York, USA); North American Cordillera (North Cascades Range, Washington; Snake Range, Nevada, USA); western Rocky Mountains (British Columbia, Canada); southern Menderes Massif (Turkey); Santander Massif (Colombia); and the Sanandaj-Sirjan zone (Hamadan, Iran). In some samples, polycrystals comprise ~20-30% of garnets analyzed, and chemical and textural evidence suggests that early coalescence of garnet polycrystals is common. Some early-coalescing polycrystals exhibit growth zoning that is concentric about the geometric center of the polycrystal. In thin section, these garnets may be undetectable as polycrystals based on morphology or zoning. In some polycrystals, zoning is unrelated to the location of internal grain boundaries; in others, Fe-Mn-Mg zoning has a different pattern than that of Ca; zoning patterns may vary on the scale of a single thin section. In addition, some polycrystals are characterized by high-angle misorientation boundaries that may be in special (non-random) orientations, an observation that indicates that these polycrystals are not random clusters of grains. The presence of internal grain boundaries may affect diffusion pathways and length scales, and may facilitate communication of porphyroblast interiors with matrix phases, thereby influencing reaction history of the rock and the composition/zoning of garnet.
Mesoscale Modeling of Dynamic Failure of Ceramic Polycrystals
2011-08-01
models are used to study dynamic deformation and failure in silicon carbide ( SiC ) and aluminum oxynitride (AlON) polycrystals. Elastic and...ABSTRACT Mesoscale models are used to study dynamic deformation and failure in silicon carbide ( SiC ) and aluminum oxynitride (AlON) polycrystals...percolation. However, the present computations omit the possibility of grain cleavage. A high purity SiC microstructure with larger grains would be
Directory of Open Access Journals (Sweden)
YANG Didi
2012-12-01
Full Text Available A heterogenous Pd(Ⅱ organometal catalyst with bicontinuous cubic Ia3d mesostructure was synthesized by surfactant-directed co-condensation of Pd［PPh2(CH22Si(OCH2CH33］2Cl2 and (CH3CH2O3SiPhSi(OCH2CH33.In water-medium Sonogashira reaction,the as-prepared Pd(Ⅱ-PMO-KIT-6 exhibited higher catalytic activity than reference catalyst Pd(Ⅱ-KIT-6 and could be used repetitively for more than 4 times,which could reduce the cost and even diminish the environmental pollution from heavy metallic ions,showing a good potential in industrial applications.
Liou, Tzong-Horng
2012-07-01
The electronics industry is one of the world's fastest growing manufacturing industries. However, e-waste has become a serious pollution problem. This study reports the recovery of e-waste for preparing valuable MCM-48 and ordered mesoporous carbon for the first time. Specifically, this study adopts an alkali-extracted method to obtain sodium silicate precursors from electronic packaging resin ash. The influence of synthesis variables such as gelation pH, neutral/cationic surfactant ratio, hydrothermal treatment temperature, and calcination temperature on the mesophase of MCM-48 materials is investigated. Experimental results confirm that well-ordered cubic MCM-48 materials were synthesized in strongly acidic and strongly basic media. The resulting mesoporous silica had a high surface area of 1,317 m2/g, mean pore size of about 3.0 nm, and a high purity of 99.87 wt%. Ordered mesoporous carbon with high surface area (1,715 m2/g) and uniform pore size of CMK-1 type was successfully prepared by impregnating MCM-48 template using the resin waste. The carbon structure was sensitive to the sulfuric acid concentration and carbonization temperature. Converting e-waste into MCM-48 materials not only eliminates the disposal problem of e-waste, but also transforms industrial waste into a useful nanomaterial.
Energy Technology Data Exchange (ETDEWEB)
Argyriou, D.N. [Australian Nuclear Science and Technology Organisation, Menai, NSW (Australia); Howard, C.J. [Australian Nuclear Science and Technology Organisation, Menai, NSW (Australia)
1995-04-01
In the re-investigation by neutron powder diffraction of 3 mol% yttria-tetragonal zirconia polycrystal (Y-TZP), it was realized that the sample, initially taken to be single-phase tetragonal zirconia, was in fact a two-phase mixture of the tetragonal (80%) and cubic (20%) polymorphs. Two-phase refinement gave for the tetragonal phase [P4{sub 2}/nmc, a = 3.6008 (1), c = 5.1793 (1) A] the results z{sub O} = 0.4564 (1), B{sub Zr,Y} = 0.45 (2) and B{sub O} = 0.72 (2) A{sup 2}. Refinement on the basis of a single-phase tetragonal sample yielded values for the position and displacement parameters somewhat biased towards those pertaining to the cubic phase. The conclusions from previous studies have been re-examined in the light of the present work. (orig.).
Nasir, Nadeem; Yahya, Noorhana; Kashif, Muhammad; Daud, Hanita; Akhtar, Majid Niaz; Zaid, Hasnah Mohd; Shafie, Afza; Teng, Lee Chaw
2011-03-01
This is our initial response towards preparation of nano-inductors garnet for high operating frequencies strontium iron garnet (Sr3Fe5O12) denoted as SrIG and yttrium iron garnet (Y3Fe5O12) denoted as YIG. The garnet nano crystals were prepared by novel sol-gel technique. The phase and crystal structure of the prepared samples were identified by using X-ray diffraction analysis. SEM images were done to reveal the surface morphology of the samples. Raman spectra was taken for yttrium iron garnet (Y3Fe5O12). The magnetic properties of the samples namely initial permeability (micro), relative loss factor (RLF) and quality factor (Q-Factor) were done by using LCR meter. From the XRD profile, both of the Y3Fe5O12 and Sr3Fe5O12 samples showed single phase garnet and crystallization had completely occurred at 900 degrees C for the SrIG and 950 degrees C for the YIG samples. The YIG sample showed extremely low RLF value (0.0082) and high density 4.623 g/cm3. Interesting however is the high Q factor (20-60) shown by the Sr3Fe5O12 sample from 20-100 MHz. This high performance magnetic property is attributed to the homogenous and cubical-like microstructure. The YIG particles were used as magnetic feeder for EM transmitter. It was observed that YIG magnetic feeder with the EM transmitter gave 39% higher magnetic field than without YIG magnetic feeder.
Electrolytic coloration of hydroxyl-doped potassium iodide polycrystals
Wang, Na; Gu, Hongen; Han, Li; Guo, Meili; Qin, Fang
2007-03-01
Hydroxyl-doped potassium iodide polycrystals were successfully colored electrolytically by using a pointed cathode and a flat anode at various temperatures and electric field strengths, which mainly benefits appropriate coloration temperatures and electric field strengths. Characteristic OH-, O2--Va+ , U, V2, V3, Cu+, Cu-related, I2- , I2, K, F, R1 and R2 spectral bands were observed in Kubelka-Munk functions of the colored polycrystals, and the OH- and O2--Va+ spectral bands at room temperature were determined from Mollwo-Ivey plots. Color center formation in the electrolytic coloration was explained.
Two stochastic mean-field polycrystal plasticity methods
Energy Technology Data Exchange (ETDEWEB)
Tonks, Michael [Los Alamos National Laboratory
2008-01-01
In this work, we develop two mean-field polycrystal plasticity models in which the L{sup c} are approximated stochastically. Through comprehensive CPFEM analyses of an idealized tantalum polycrystal, we verify that the L{sup c} tend to follow a normal distribution and surmise that this is due to the crystal interactions. We draw on these results to develop the STM and the stochastic no-constraints model (SNCM), which differ in the manner in which the crystal strain rates D{sup c} are prescribed. Calibration and validation of the models are performed using data from tantalum compression experiments. Both models predict the compression textures more accurately than the FCM, and the SNCM predicts them more accurately than the STM. The STM is extremely computationally efficient, only slightly more expensive than the FCM, while the SNCM is three times more computationally expensive than the STM.
DEFF Research Database (Denmark)
Huang, X.; Borrego, A.; Pantleon, W.
2001-01-01
of microstructures have been identified. A correlation is found between microstructure and grain orientation, which agrees well with earlier observations in tensile deformed aluminum polycrystals and copper single crystals. The stress–strain curve of the copper polycrystal is calculated with good accuracy from...... single crystal data, which are weighted according to the volume fractions of the three different types based on a quantitative texture measurement of the polycrystal....
Energy Technology Data Exchange (ETDEWEB)
Zhang, Yanhua; Cai, Jin [State Key Lab of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Chen, Fei, E-mail: chenfei027@gmail.com [State Key Lab of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Massachusetts Institute of Technology, 77 Massachusetts Avenue, W20-021 Cambridge, MA 02139-4307 (United States); Tu, Rong; Shen, Qiang; Zhang, Xulong [State Key Lab of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Zhang, Lianmeng [State Key Lab of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Massachusetts Institute of Technology, 77 Massachusetts Avenue, W20-021 Cambridge, MA 02139-4307 (United States)
2015-09-25
Highlights: • A core–shell nano-sized precursor was synthesized by a two-step precipitation. • Cubic LLZO dense body was obtained at low temperatures by the novel precursor. • The cubic LLZO sintered body showed an extremely high Li ionic conductivity. - Abstract: Nano-sized Al-doped Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12} (LLZO) precursor is successfully synthesized by a novel two-step precipitation method. Microstructure and thermal behavior of the prepared LLZO precursor powders and properties of the sintered LLZO pellets are comprehensively investigated. Results show that the obtained precursor powders have a special core–shell structure that a coating of Li{sub 2}C{sub 2}O{sub 4} covers on the surface of the lanthanum and zirconium co-precipitate products. Pure cubic LLZO powders can be obtained at a low calcination temperature of 900 °C. Sample sintered by field assisted sintering technology at 1000 °C has a high relative density of 96.5% with a total ionic conductivity of as high as 3.32 × 10{sup −4} S cm{sup −1} (corresponding to the activation energy of 0.32 eV) at room temperature. The reported method provides a simple and low-temperature synthesis of high quality LLZO solid electrolytes.
Energy Technology Data Exchange (ETDEWEB)
Swab, J.J. [Army Materials Research Agency, Watertown, MA (United States). Materials Technology Lab.
1989-03-01
Seven commercially available yttria-tetragonal zirconia polycrystal (Y-TZP) materials were evaluated. Room temperature properties were measured before and after heat treatments at 1000C. Microstructure and phase stability were also examined. In all but one case, the Y-TZPs showed very little change in room temperature properties after long times at this temperature. Results show that pressure-assisted processing greatly improves the strength by reducing porosity and keeping the grain size extremely fine, but this reduces the toughness because finer grains are more difficult to transform. In addition, a small amount of cubic zirconia appears to enhance the toughness of fine-grained Y-TZP while maintaining good strength. During processing, a small amount of cubic zirconia is formed and allowed to grow. This creates regions poor in yttria which can transform spontaneously in the presence of a crack-tip stress field.
Effects of Al additives on growth of GaN polycrystals by the Na flux method
Imabayashi, Hiroki; Murakami, Kosuke; Matsuo, Daisuke; Honjo, Masatomo; Imanishi, Masayuki; Maruyama, Mihoko; Imade, Mamoru; Yoshimura, Masashi; Mori, Yusuke
2017-03-01
In this study, we investigated the growth of GaN polycrystals using the Al-added Na flux method. We studied the effects of Al on accelerating the nucleation and purity of GaN polycrystals. The yields of GaN crystals grown in Al-added Na flux were dramatically increased from those in Al-free Na flux, and the polycrystals grown by the Al-added Na flux method were highly transparent. As observed in secondary ion mass spectroscopy measurements, the Al content of the polycrystals was below the detection limit of 3 × 1016 atoms/cm3. From these results, the Al-added Na flux method is found to be appropriate for fabricating a large amount of GaN polycrystals without deteriorating the crystal quality.
Cubic Subalgebras and Cubic Closed Ideals of B-algebras
Directory of Open Access Journals (Sweden)
Tapan Senapati
2015-06-01
Full Text Available In this paper, the concept of cubic set to subalgebras, ideals and closed ideals of B-algebras are introduced. Relations among cubic subalgebras with cubic ideals and cubic closed ideals of B-algebras investigated. The homomorphic image and inverse image of cubic subalgebras, ideals are studied and some related properties are investigated. Also, the product of cubic B-algebras are investigated.
GREEN＇S FUNCTION AND EFFECTIVE ELASTIC STIFFNESS TENSOR FOR ARBITRARY AGGREGATES OF CUBIC CRYSTALS
Institute of Scientific and Technical Information of China (English)
HuangMojia; ZhengChaomei
2004-01-01
A closed but approximate formula of Green's function for an arbitrary aggregate of cubic crystallites is given to derive the effective elastic stiffness tensor of the polycrystal. This formula, which includes three elastic constants of single cubic crystal and five texture coefficients,accounts for the effects of the orientation distribution function (ODF) up to terms linear in the texture coefficients. Thus it is expected that our formula would be applicable to arbitrary aggregates with weak texture or to materials such as aluminum whose single crystal has weak anisotropy.Three examples are presented to compare predictions from our formula with those from Nishioka and Lothe's formula and Synge's contour integral through numerical integration. As an application of Green's function, we briefly describe the procedure of deriving the effective elastic stiffness tensor for an orthorhombic aggregate of cubic crystallites. The comparison of the computational results given by the finite element method and our effective elastic stiffness tensor is made by an example.
Tetragonal zirconia polycrystals - a high performance solid oxygen ion conductor. [ZrO[sub 2
Energy Technology Data Exchange (ETDEWEB)
Weppner, W. (Max-Planck-Inst. fuer Festkoerperforschung, Stuttgart (Germany))
1992-05-01
The ionic conductivity of sintered pellets of tetragonal zirconia polycrystals (TZP) was found to be higher than that of cubic stabilized zirconia (CSZ) below about 700degC in spite of the lower concentration of defects. At 400degC the bulk conductivity is 1.2 X 10[sup -4] [Omega][sup -1] cm[sup -1] with an activation enthalpy of 0.92 eV. This shows that the mobility of the defects in TZP is about one order of magnitude higher than in CSZ. TZP pellets show high thermo-mechanical stability and may be readily sealed into glass tubes to provide gastight separate electrode compartments. Such an arrangement shows a fast response to variations of the oxygen partial pressure even at temperatures as low as 150degC. The correct Nernstian voltage is observed within about 1 s under reducing conditions and within a few minutes under oxidizing conditions. It may be assumed that the fast response even at low temperatures is related to the electronic properties of TZP. Investigations of the electronic behavior of the surface by work function measurements and of the minority charge carrier conductivities are reported as a function of the temperature and oxygen partial pressure. The evaluation of Hebb-Wagner polarization measurements has to be modified by considering the formation of internal electrical fields. It appears that TZP is very useful for fuel cells in view of both its thermo-mechanical stability and its favorable electrical properties at lower temperatures. Limiting-current oxygen sensors have been developed on the basis of this material which show superior performance compared with CSZ. Replacement of the gas diffusion barrier by a solid oxide allows high oxygen partial pressure to be measured.
A finite element model of ferroelectric/ferroelastic polycrystals
Energy Technology Data Exchange (ETDEWEB)
HWANG,STEPHEN C.; MCMEEKING,ROBERT M.
2000-02-17
A finite element model of polarization switching in a polycrystalline ferroelectric/ferroelastic ceramic is developed. It is assumed that a crystallite switches if the reduction in potential energy of the polycrystal exceeds a critical energy barrier per unit volume of switching material. Each crystallite is represented by a finite element with the possible dipole directions assigned randomly subject to crystallographic constraints. The model accounts for both electric field induced (i.e. ferroelectric) switching and stress induced (i.e. ferroelastic) switching with piezoelectric interactions. Experimentally measured elastic, dielectric, and piezoelectric constants are used consistently, but different effective critical energy barriers are selected phenomenologically. Electric displacement versus electric field, strain versus electric field, stress versus strain, and stress versus electric displacement loops of a ceramic lead lanthanum zirconate titanate (PLZT) are modeled well below the Curie temperature.
Energy Technology Data Exchange (ETDEWEB)
Wang Fen [Department of Physics, Tianjin University, Tianjin 300072 (China); Gu Hongen, E-mail: jthgu@163.co [Department of Physics, Tianjin University, Tianjin 300072 (China); Qin Fang [Department of Physics, Chengde National Teacher' s College, Chengde 067000 (China); Liu Jia; Chen Weiwei [Department of Physics, Tianjin University, Tianjin 300072 (China)
2010-02-01
OH{sup -}-doped KCl polycrystals are colored electrolytically by using a pointed cathode and a flat anode at various temperatures and voltages. Characteristic O{sup -}, OH{sup -}, U, U{sub A} and Cu{sup +} absorption peaks are observed in resolved absorption spectra of uncolored polycrystals. Characteristic V{sub 2}, V{sub 3}, Cu{sup +}, O{sup 2-}-V{sub a}{sup +}, I{sub 2}{sup -}, I{sub 2}, H{sub 2}O{sup -} and F spectral bands are observed at room temperature in Kubelka-Munk functions of colored polycrystals. Current-time curve for electrolytic coloration of an OH{sup -}-doped KCl polycrystal and its relationship with electrolytic coloration process are given. Production and conversion of color centers are explained.
Electrolytic coloration and spectral properties of OH{sup -}-doped KBr polycrystals
Energy Technology Data Exchange (ETDEWEB)
Gu Hongen, E-mail: jthgu@163.co [Department of Physics, Tianjin University, Tianjin 300072 (China); Liu Jia [Department of Physics, Tianjin University, Tianjin 300072 (China); Qin Fang [Department of Physics, Chengde National Teacher' s College, Chengde 067000 (China); Wang Fen; Chen Weiwei [Department of Physics, Tianjin University, Tianjin 300072 (China)
2009-08-01
OH{sup -}-doped KBr polycrystals were colored electrolytically by using a pointed cathode and a flat anode. Characteristic O{sup -}, OH{sup -}, U, Cu{sup +} and O{sup 2-}-V{sub a}{sup +} absorption peaks were observed in resolved absorption spectrum of uncolored polycrystals. Herein the position of the O{sup 2-}-V{sub a}{sup +} absorption peak at room temperature was determined by using a Mollwo-Ivey plot. Characteristic V{sub 2}, V{sub 3}, Cu{sup +}, O{sup 2-}-V{sub a}{sup +},I{sub 2}{sup -}, I{sub 2} and F spectral bands were observed in Kubelka-Munk functions of colored polycrystals. Current-time curve for electrolytic coloration of an OH{sup -}-doped KBr polycrystal and its relationship with electrolytic coloration process were given. Formation and conversion of color centers were explained.
Bueno, Pablo; Cano, Pablo A.
2016-11-01
We drastically simplify the problem of linearizing a general higher-order theory of gravity. We reduce it to the evaluation of its Lagrangian on a particular Riemann tensor depending on two parameters, and the computation of two derivatives with respect to one of those parameters. We use our method to construct a D -dimensional cubic theory of gravity which satisfies the following properties: (1) it shares the spectrum of Einstein gravity, i.e., it only propagates a transverse and massless graviton on a maximally symmetric background; (2) it is defined in the same way in general dimensions; (3) it is neither trivial nor topological in four dimensions. Up to cubic order in curvature, the only previously known theories satisfying the first two requirements are the Lovelock ones. We show that, up to cubic order, there exists only one additional theory satisfying requirements (1) and (2). Interestingly, this theory is, along with Einstein gravity, the only one which also satisfies (3).
DEFF Research Database (Denmark)
Birkedal, Lars; Bizjak, Aleš; Clouston, Ranald;
2016-01-01
This paper improves the treatment of equality in guarded dependent type theory (GDTT), by combining it with cubical type theory (CTT). GDTT is an extensional type theory with guarded recursive types, which are useful for building models of program logics, and for programming and reasoning with co...
Institute of Scientific and Technical Information of China (English)
苏旬; 贺秀丽; 刘秀菊; 郭京艳; 翟光喜
2012-01-01
目的:制备姜黄素脂质立方液晶纳米粒,并对其主要理化性质进行评价.方法:采用热处理高压匀质法进行制备,以载药量和包封率为指标,采用均匀设计法对处方和工艺进行优化,并考察其理化性质.结果:制得的液晶纳米粒在电镜下呈类球形,平均粒径176.1 nm,zeta电位-25.19 mV,平均载药量(1.5±0.2)％,包封率(95±1.8)％,36 h体外释放60.0％,释放方程为In(1-Q)=-0.0251t-0.0075.结论:姜黄素脂质立方液晶纳米粒具有较高的包封率和良好的缓释作用.%Objective: To prepare curcumin-loaded lipid cubic liquid crystalline nanoparticles and evaluate its physiochemical properties. Methods:The nanoparticles were prepared using hot and high-pressure homogenization. The prescription and preparation process were optimized by uniform design with drug loading and entrapment efficiency as indexes. Results: The nanoparticles were spherical under transmission electron microscope (TEM) with average particle size of 176. 1 nm, zeta potential of -25.19 mV, average drug loading of (1. 5 ±0. 2) % and entrapment efficiency of (95 ±1.8)%. The release equation; In( 1 - Q) = -0.0251t-0.0075. The cumulative release percentage was 60% at 36 h in vitro. Conclusion:The obtained curcumin-loaded lipid cubic liquid crystalline nanoparticles shows high entrapment efficiency and good sustain release property.
Propagation of elastic waves through textured polycrystals: application to ice.
Maurel, Agnès; Lund, Fernando; Montagnat, Maurine
2015-05-08
The propagation of elastic waves in polycrystals is revisited, with an emphasis on configurations relevant to the study of ice. Randomly oriented hexagonal single crystals are considered with specific, non-uniform, probability distributions for their major axis. Three typical textures or fabrics (i.e. preferred grain orientations) are studied in detail: one cluster fabric and two girdle fabrics, as found in ice recovered from deep ice cores. After computing the averaged elasticity tensor for the considered textures, wave propagation is studied using a wave equation with elastic constants c=〈c〉+δc that are equal to an average plus deviations, presumed small, from that average. This allows for the use of the Voigt average in the wave equation, and velocities are obtained solving the appropriate Christoffel equation. The velocity for vertical propagation, as appropriate to interpret sonic logging measurements, is analysed in more details. Our formulae are shown to be accurate at the 0.5% level and they provide a rationale for previous empirical fits to wave propagation velocities with a quantitative agreement at the 0.07-0.7% level. We conclude that, within the formalism presented here, it is appropriate to use, with confidence, velocity measurements to characterize ice fabrics.
DEFF Research Database (Denmark)
Birkedal, Lars; Bizjak, Aleš; Clouston, Ranald;
2016-01-01
This paper improves the treatment of equality in guarded dependent type theory (GDTT), by combining it with cubical type theory (CTT). GDTT is an extensional type theory with guarded recursive types, which are useful for building models of program logics, and for programming and reasoning...... with coinductive types. We wish to implement GDTT with decidable type-checking, while still supporting non-trivial equality proofs that reason about the extensions of guarded recursive constructions. CTT is a variation of Martin-L\\"of type theory in which the identity type is replaced by abstract paths between...... terms. CTT provides a computational interpretation of functional extensionality, is conjectured to have decidable type checking, and has an implemented type-checker. Our new type theory, called guarded cubical type theory, provides a computational interpretation of extensionality for guarded recursive...
DEFF Research Database (Denmark)
Birkedal, Lars; Bizjak, Aleš; Clouston, Ranald;
2016-01-01
This paper improves the treatment of equality in guarded dependent type theory (GDTT), by combining it with cubical type theory (CTT). GDTT is an extensional type theory with guarded recursive types, which are useful for building models of program logics, and for programming and reasoning...... with coinductive types. We wish to implement GDTT with decidable type checking, while still supporting non-trivial equality proofs that reason about the extensions of guarded recursive constructions. CTT is a variation of Martin-L\\"of type theory in which the identity type is replaced by abstract paths between...... terms. CTT provides a computational interpretation of functional extensionality, enjoys canonicity for the natural numbers type, and is conjectured to support decidable type-checking. Our new type theory, guarded cubical type theory (GCTT), provides a computational interpretation of extensionality...
Li, Xinkai; Wang, Jie
2017-01-01
The effect of grain size on the domain structures and electromechanical responses of ferroelectric polycrystals is investigated by a phase field model. The phase field simulations show that the different types of domains in different size of grains play an important role in the size-dependent properties of ferroelectric polycrystals. It is found that the remnant polarization, coercive field and dielectric coefficient increase monotonously with the increase of grain size. However, the piezoelectric coefficient increases first and then decreases as the grain size increases. The decrease of vortex domains is responsible for the increase of piezoelectric coefficient in the range of small grain size, the decrease of 90° domain walls results in the decrease of piezoelectric coefficient in the range of large grain size. In addition, different domain structures in different size of grains have also great influence on the mechanical depolarization of the ferroelectric polycrystals subjected to a compressive stress.
Institute of Scientific and Technical Information of China (English)
徐锋; 左敦稳; 张旭辉; 户海峰; 张骋; 王珉
2013-01-01
Cubic Boron Nitride(cBN) is a super-hard material, of which hardness is only less than diamond. But it has excellent chemical stability, especially no chemical reaction with ferrous materials. The cBN coating has irreplaceable function in the application of modern cutting tools. Research is carried out on the preparation of cBN coating on YG6 by micro/nanocrystalline diamond (M/NCD) film inter-layer. The micro/nanocrystalline diamond film is deposited in hot filament chemical vapor deposition system and cBN is deposited in radio frequency magnetron sputtering system. The scanning electron microscopy (SEM), Raman, atomic force microscopy(AFM), Fourier transferred infrared(FTIR) and in-denter are used to investigate the content, morphology and adhesion of the coating. The results show that the adhesion of cBN coating on WC-Co by micro/nanocrystalline diamond interlayer is much higher than that by nano diamond interlayer. The moderate bias voltage is important for the cBN film deposition in the magnetron sputtering process.%立方氮化硼(Cubic Boron Nitride,cBN)是仅次于金刚石的超硬材料,比金刚石具有更高的化学稳定性,可以胜任铁系金属的加工.本文在YG6硬质合金上基于微纳米金刚石过渡层开展cBN涂层的制备研究.本文在热丝化学气相沉积系统中制备微纳米金刚石过渡层(Micro/nanocrystalline diamond,M/NCD),在射频磁控溅射系统中制备cBN涂层,并对M/NCD与cBN涂层进行了成分、微观形貌与结合性能的研究.研究结果发现,在硬质合金基体上,M/NCD过渡层的结合性能明显优于NCD过渡层.磁控溅射制备cBN涂层过程中,存在适合cBN沉积的衬底偏压阈值,过高或过低的衬底偏压均不利于cBN含量的提高.
Green Upconversion Luminescence in Er3+/Yb3+ Codoped CaWO4 Polycrystals
Institute of Scientific and Technical Information of China (English)
XU Yan-Ling; ZHAO Hong; WANG Rui; ZHANG Chun-Yu
2011-01-01
CaWO4 polycrystals with fixed Yb3+ and various Ei2* concentrations are synthesized via the high temperature solid state method. The crystal structure of the polycrystals is characterized by means of x-ray diffraction. The upconversion properties of the polycrystals under the 980 nm excitation are investigated. Intense emission bands centered at 530nm and 552nm correspond to the transitions 2H11/2 → 4hs/2 and 4S3/2→ 4hs/2 of Er3+, respectively. The dependence of intensity of the green emission on the pump power and possible upconversion mechanism are discussed. Quantitative analysis of dependence of upconversion emission intensity on the pump power of a laser diode indicates that two-photon processes are responsible for both 530 nm and 552 nm green upconversion emissions.%@@ CAWO polycrystals with fixed Yb and various Er concentrations are synthesized via the high temperature solid state method.The crystal structure of the polycrystals is characterized by means of x-ray diffraction.The upconversion properties of the polycrystals under the 980 nm excitation are investigated.Intense emission bands centered at 530hm and 552nm correspond to the transitions H → I and S → I of Er, respectively.The dependence of intensity of the green emission on the pump power and possible upconversion mechanism are discussed.Quantitative analysis of dependence of upconversion emission intensity on the pump power of a laser diode indicates that two-photon processes are responsible for both 530hm and 552nm green upconversion emissions.
Hysteresis and relaxation in TlBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub y} superconducting polycrystals
Energy Technology Data Exchange (ETDEWEB)
Batista-Leyva, A J [Physics Department, Engineering Faculty, University of Holguin, Holguin 80100 (Cuba); Cobas, R [Superconductivity Laboratory, IMRE-Physics Faculty, University of Havana, 10400 Havana (Cuba); Orlando, M T D [Physics Department, Universidade Federal do Espiritu Santo, Vitoria ES 29060-900 (Brazil); Altshuler, E [Superconductivity Laboratory, IMRE-Physics Faculty, University of Havana, 10400 Havana (Cuba)
2003-08-01
We study the hysteresis and relaxation of both intragranular and intergranular properties of TlBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub y} (Tl-1223) superconducting polycrystals between 80 and 120 K. The samples have been prepared using a technique involving the mixing of grains of different sizes before the final sintering. The grains show a sizeable reversible magnetization, while vortices inside the grain behave as three-dimensional objects. The transport critical current is strongly hysteretic, with features that distinguish our Tl-1223 samples from 'standard' YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO), (Hg, Re)Ba{sub 2}Ca{sub 2}Cu{sub 3}O{sub 8+{delta}} (HBCCO) and (Bi, Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10-{delta}} (BSCCO) polycrystals. The preparation method improves the transport properties of the samples. The relaxation of the transport critical current density, in the presence of trapped fields, is reported here for the first time in this system, as far as we know. A phenomenological model can qualitatively describe the transport properties, where the intragrain magnetization affects the intergranular junctions, but a precise quantitative description is not achieved. The differences in the shape of the transport measurements, for different polycrystalline systems, are also well described by the model.
Anisotropic cubic curvature couplings
Bailey, Quentin G
2016-01-01
To complement recent work on tests of spacetime symmetry in gravity, cubic curvature couplings are studied using an effective field theory description of spacetime-symmetry breaking. The associated mass dimension 8 coefficients for Lorentz violation studied do not result in any linearized gravity modifications and instead are revealed in the first nonlinear terms in an expansion of spacetime around a flat background. We consider effects on gravitational radiation through the energy loss of a binary system and we study two-body orbital perturbations using the post-Newtonian metric. Some effects depend on the internal structure of the source and test bodies, thereby breaking the Weak Equivalence Principle for self-gravitating bodies. These coefficients can be measured in solar-system tests, while binary-pulsar systems and short-range gravity tests are particularly sensitive.
A strain gradient crystal plasticity analysis of grain size effects in polycrystals
DEFF Research Database (Denmark)
Borg, Ulrik
2007-01-01
individually oriented grains, in a unit cell, each having three planar slip systems. An energy potential that penalizes crystallographic slip at grain boundaries is included in the analyzes. The polycrystal is subjected to plane strain tension for various grain sizes and higher order boundary conditions...
Boutz, M.M.R.; Boutz, M.M.R.; Winnubst, Aloysius J.A.; Burggraaf, Anthonie; Burggraaf, A.J.
1994-01-01
An analysis is presented of grain growth and densification of yttria-ceria stabilized tetragonal zirconia polycrystals (Y, Ce-TZPs) using both isothermal and non-isothermal techniques. The characteristics of Y, Ce-TZPs are compared to those of Y-TZP and Ce-TZP and the effect of increasing ceria
A greedy method for reconstructing polycrystals from three-dimensional X-ray diffraction data
DEFF Research Database (Denmark)
Kulshreshth, Arun Kumar; Alpers, Andreas; Herman, Gabor T.
2009-01-01
An iterative search method is proposed for obtaining orientation maps inside polycrystals from three-dimensional X-ray diffraction (3DXRD) data. In each step, detector pixel intensities are calculated by a forward model based on the current estimate of the orientation map. The pixel at which the ...
Berryman, James G.; Grechka, Vladimir
2006-12-01
A model study on fractured systems was performed using a concept that treats isotropic cracked systems as ensembles of cracked grains by analogy to isotropic polycrystalline elastic media. The approach has two advantages: (a) Averaging performed is ensemble averaging, thus avoiding the criticism legitimately leveled at most effective medium theories of quasistatic elastic behavior for cracked media based on volume concentrations of inclusions. Since crack effects are largely independent of the volume they occupy in the composite, such a non-volume-based method offers an appealingly simple modeling alternative. (b) The second advantage is that both polycrystals and fractured media are stiffer than might otherwise be expected, due to natural bridging effects of the strong components. These same effects have also often been interpreted as crack-crack screening in high-crack-density fractured media, but there is no inherent conflict between these two interpretations of this phenomenon. Results of the study are somewhat mixed. The spread in elastic constants observed in a set of numerical experiments is found to be very comparable to the spread in values contained between the Reuss and Voigt bounds for the polycrystal model. Unfortunately, computed Hashin-Shtrikman bounds are much too tight to be in agreement with the numerical data, showing that polycrystals of cracked grains tend to violate some implicit assumptions of the Hashin-Shtrikman bounding approach. However, the self-consistent estimates obtained for the random polycrystal model are nevertheless very good estimators of the observed average behavior.
碘化铟（InI）多晶的水平区熔提纯%Horizontal Zone Refining of Indium Iodide (InI) Polycrystal
Institute of Scientific and Technical Information of China (English)
徐朝鹏; 张磊; 王倩; 纪亮亮; 李亚可
2015-01-01
The indium iodide (InI) polycrystal which was synthesized by two-zone vapor transporting method was purified by using horizontal zone refining method. Preparation process on high quality and single phase InI polycrystal was successfully fixed. The lattice structure, morphology, component and impuritily concentration of InI crystal were investigated by X-Ray Diffraction (XRD), Scanning Electron Microscope-Energy Dispersive Spectrometer (SEM-EDS) and Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). The re-sults indicate that the InI polycrystal after refinement has better lattice structure and higher quality than before. The lattice constants ofa,b andc are 0.476 nm, 1.278 nm and 0.491 nm, respectively, which are very close to the theoretical values. The stoichiometric ratio of In to I is effectively modified and close to the theoretical stoichiometric ratio 1:1. The intermediate products and impurities concentrations decrease significantly. An InI single crystal with high resistivity (about 1010Ω·cm) is grown by Czochralski (CZ) method with the purified InI polycrystal obtained in this work.%采用水平区熔法对由两温区气相输运法制备的InI多晶进行提纯,探索高纯、单相InI多晶的制备工艺。通过 X 射线粉末衍射仪、扫描电子显微镜以及电感耦合等离子体原子发射光谱仪对水平区熔提纯前后的 InI 多晶的晶格结构、形貌组分以及杂质浓度进行了表征。结果表明,经过水平区熔提纯后的InI多晶晶格结构完整,质量较高,晶格参数为a=0.476 nm,b=1.278 nm,c=0.491 nm,与理论值十分接近； In、I化学配比得到了有效调节,其化学配比接近理论化学配比1：1；中间产物含量及杂质浓度显著降低。以提纯后InI多晶为原料,用提拉法生长出的InI单晶电阻率达到1010Ω·cm。
Magnetostrictive distortion in Pr0.15TbxDy0.85-xFe2 polycrystals by X-ray diffraction
Institute of Scientific and Technical Information of China (English)
MENG Fan-bin; LI Yang-xian; CHEN Gui-feng; LIU He-yan; QU Jing-ping; CHEN Jing-lan; WU Guang-heng
2005-01-01
The ingots of Pr0.15TbxDy0.85-xFe2 (x=0.100.85) series compounds with a single phase were prepared by a arc melting method. The X-ray diffraction patterns were measured using a Philips Xpert MPD X-ray diffractometer with a non-ambient sample stage at different temperatures, the magnetostrictive distortion in Pr0.15TbxDy0.85-xFe2 polycrystals was investigated by X-ray diffraction patterns and the magnetostriction coefficient λ111 was calculated. The results show when the temperature is raised above the spin reorientation temperature region, a splitting appears in the reflection (440); the λ111 increase with the increasing of Tb content for Pr0.15TbxDy0.85-xFe2 polycrystals and the full width at half maximum (FWHM) of the reflection (440) increases gradually with the increasing of Tb content. Moreover, as the FWHM of the reflection (440) decreases gradually with the increasing of temperature, the λ111 decreases slightly with the increasing of temperature at the temperature region of 223373 K for Pr0.15Tb0.3Dy0.55Fe2 alloy.
Method of synthesizing cubic system boron nitride
Energy Technology Data Exchange (ETDEWEB)
Yuzu, S.; Sumiya, H.; Degawa, J.
1987-10-13
A method is described for synthetically growing cubic system boron nitride crystals by using boron nitride sources, solvents for dissolving the boron nitride sources, and seed crystals under conditions of ultra-high pressure and high temperature for maintaining the cubic system boron nitride stable. The method comprises the following steps: preparing a synthesizing vessel having at least two chambers, arrayed in order in the synthesizing vessel so as to be heated according to a temperature gradient; placing the solvents having different eutectic temperatures in each chamber with respect to the boron nitride sources according to the temperature gradient; placing the boron nitride source in contact with a portion of each of the solvents heated at a relatively higher temperature and placing at least a seed crystal in a portion of each of the solvents heated at a relatively lower temperature; and growing at least one cubic system boron nitride crystal in each of the solvents in the chambers by heating the synthesizing vessel for establishing the temperature gradient while maintaining conditions of ultra-high pressure and high temperature.
National Research Council Canada - National Science Library
Goodwin, Adrian N
2009-01-01
A flexible tree taper model based on a cubic polynomial is described. It is algebraically invertible and integrable, and can be constrained by one or two diameters, neither of which need be diameter at breast height (DBH...
Ultrahard nanotwinned cubic boron nitride.
Tian, Yongjun; Xu, Bo; Yu, Dongli; Ma, Yanming; Wang, Yanbin; Jiang, Yingbing; Hu, Wentao; Tang, Chengchun; Gao, Yufei; Luo, Kun; Zhao, Zhisheng; Wang, Li-Min; Wen, Bin; He, Julong; Liu, Zhongyuan
2013-01-17
Cubic boron nitride (cBN) is a well known superhard material that has a wide range of industrial applications. Nanostructuring of cBN is an effective way to improve its hardness by virtue of the Hall-Petch effect--the tendency for hardness to increase with decreasing grain size. Polycrystalline cBN materials are often synthesized by using the martensitic transformation of a graphite-like BN precursor, in which high pressures and temperatures lead to puckering of the BN layers. Such approaches have led to synthetic polycrystalline cBN having grain sizes as small as ∼14 nm (refs 1, 2, 4, 5). Here we report the formation of cBN with a nanostructure dominated by fine twin domains of average thickness ∼3.8 nm. This nanotwinned cBN was synthesized from specially prepared BN precursor nanoparticles possessing onion-like nested structures with intrinsically puckered BN layers and numerous stacking faults. The resulting nanotwinned cBN bulk samples are optically transparent with a striking combination of physical properties: an extremely high Vickers hardness (exceeding 100 GPa, the optimal hardness of synthetic diamond), a high oxidization temperature (∼1,294 °C) and a large fracture toughness (>12 MPa m(1/2), well beyond the toughness of commercial cemented tungsten carbide, ∼10 MPa m(1/2)). We show that hardening of cBN is continuous with decreasing twin thickness down to the smallest sizes investigated, contrasting with the expected reverse Hall-Petch effect below a critical grain size or the twin thickness of ∼10-15 nm found in metals and alloys.
Prakash, A.; Lebensohn, R. A.
2009-09-01
In this work, we compare finite element and fast Fourier transform approaches for the prediction of the micromechanical behavior of polycrystals. Both approaches are full-field approaches and use the same visco-plastic single crystal constitutive law. We investigate the texture and the heterogeneity of the inter- and intragranular stress and strain fields obtained from the two models. Additionally, we also look into their computational performance. Two cases—rolling of aluminum and wire drawing of tungsten—are used to evaluate the predictions of the two models. Results from both the models are similar, when large grain distortions do not occur in the polycrystal. The finite element simulations were found to be highly computationally intensive, in comparison with the fast Fourier transform simulations. Figure 9 was corrected in this article on the 25 August 2009. The corrected electronic version is identical to the print version.
Simulation of micromechanical behavior of polycrystals: finite elements vs. fast Fourier transforms
Energy Technology Data Exchange (ETDEWEB)
Lebensohn, Ricardo A [Los Alamos National Laboratory; Prakash, Arun [IWM FREIBURG
2009-01-01
In this work, we compare finite element and fast Fourier transform approaches for the prediction of micromechanical behavior of polycrystals. Both approaches are full-field approaches and use the same visco-plastic single crystal constitutive law. We investigate the texture and the heterogeneity of the inter- and intragranular, stress and strain fields obtained from the two models. Additionally, we also look into their computational performance. Two cases - rolling of aluminium and wire drawing of tungsten - are used to evaluate the predictions of the two mode1s. Results from both the models are similar, when large grain distortions do not occur in the polycrystal. The finite element simulations were found to be highly computationally intensive, in comparison to the fast Fourier transform simulations.
Institute of Scientific and Technical Information of China (English)
Chuantao Hou; Zhenhuan Li; Minsheng Huang; Chaojun Ouyang
2009-01-01
A two-dimensional discrete dislocation dynamics (DDD) technology by Giessen and Needleman (1995), which has been extended by integrating a dislocation-grain boundary interaction model, is used to computationally analyze the micro-cyclic plastic response of polycrystals containing micron-sized grains, with special attentions to significant influence of dislocationpenetrable grain boundaries (GBs) on the micro-plastic cyclic responses of polycrystals and underlying dislocation mechanism. Toward this end, a typical polycrystalline rectangular specimen under simple tension-compression loading is considered. Results show that, with the increase of cycle accumulative strain, continual dislocation accumulation and enhanced dislocation-dislocation interactions induce the cyclic hardening behavior; however, when a dynamic balance among dislocation nucleation, penetration through GB and dislocation annihilation is approximately established, cyclic stress gradually tends to saturate. In addition, other factors, including the grain size, cyclic strain amplitude and its history, also have considerable influences on the cyclic hardening and saturation.
Simas, P.; Castillo-Rodríguez, Miguel; Nó, M. L.; De-Bernardi, S.; Gómez-García, D.; Domínguez-Rodríguez, Alejandro; San Juan, J.
2014-01-01
This work focuses on the high-temperature mechanic properties of a 3 mol % yttria zirconia polycrystals (3YTZP), fabricated by hot-pressureless sintering. Systematic measurements of mechanical loss as a function of temperature and frequency were performed. An analytical method, based on the generalised Maxwell rheological model, has been used to analyse the high temperature internal friction background (HTB). This method has been previously applied to intermetallic compounds...
Zhou, Jie E.; Yan, Yongke; Priya, Shashank; Wang, Yu U.
2017-02-01
Quantitative relationships between processing, microstructure, and properties in textured ferroelectric polycrystals and the underlying responsible mechanisms are investigated by phase field modeling and computer simulation. This study focuses on three important aspects of textured ferroelectric ceramics: (i) grain microstructure evolution during templated grain growth processing, (ii) crystallographic texture development as a function of volume fraction and seed size of the templates, and (iii) dielectric and piezoelectric properties of the obtained template-matrix composites of textured polycrystals. Findings on the first two aspects are presented here, while an accompanying paper of this work reports findings on the third aspect. In this paper, grain microstructure evolution in the polycrystalline matrix with different template volume fractions and seed sizes is simulated. To quantitatively characterize the crystallographic texture development during templated grain growth processing, a numerical algorithm is developed to compute the diffraction peak intensities and Lotgering factor of the simulated polycrystals during grain microstructure evolution. This novel approach provides a direct link between phase field simulation and diffraction experiment. This computational study clarifies the effects of the template volume fraction and template seed size on the final grain microstructure and texture. It is found that, while the degree of crystallographic texture generally increases with increasing template volume fraction, it is the average distance between template seeds that plays an important role. This finding suggests that reducing the template seed size and shortening the seed distance is an effective way to achieve higher texture at a lower template volume fraction, which is highly desired for enhancing the piezoelectric properties of ferroelectric polycrystals. The computational results are compared with complementary experiments, where good agreement is
Energy Technology Data Exchange (ETDEWEB)
Battaile, C.C.; Buchheit, T.E.; Holm, E.A.; Neilsen, M.K.; Wellman, G.W.
1999-01-12
The microstructural evolution of heavily deformed polycrystalline Cu is simulated by coupling a constitutive model for polycrystal plasticity with the Monte Carlo Potts model for grain growth. The effects of deformation on boundary topology and grain growth kinetics are presented. Heavy deformation leads to dramatic strain-induced boundary migration and subsequent grain fragmentation. Grain growth is accelerated in heavily deformed microstructures. The implications of these results for the thermomechanical fatigue failure of eutectic solder joints are discussed.
Viscoplastic behavior of multiphase Earth mantle polycrystals inferred from micromechanical modeling
Castelnau, O.; Detrez, F.; Bollinger, C.; Cordier, P.; Hilairet, N.; Merkel, S.; Raterron, P. C.
2012-12-01
The strongly anisotropic rheology of olivine and pyroxene single grains, associated to polycrystal microstructures, constitutes a key feature affecting the dynamics of the Earth's upper mantle. High pressure deformation experiments carried out on olivine single crystals under synchrotron radiation, together with estimations of lattice friction based on first-principle calculations, show a transition from easy [100] to easy [001] slips in olivine as pressure and temperature (thus depth) increases. Besides dislocation glide, diffusion related deformation mechanisms such as dislocation climb, diffusion creep, and grain boundary sliding cannot be completely ruled out. Since their behavior is poorly known, they are grouped into a single isotropic viscous component. We input these elementary deformation mechanisms into a mean-field homogenization scheme (second-order self-consistent scheme of Ponte-Castaneda). This model presents the advantage of accurately predicting the mechanical interaction between deforming grains, as attested by many comparisons with full-field modeling on various polycrystals and 2-phases composites. The model has been adapted for predicting the viscoplastic behavior of olivine and olivine-pyroxene polycrystalline aggregates. Results illustrating the respective activation of elementary deformation mechanisms, but also the effect on texture evolution along several flow paths representative for in situ conditions, will be presented. It is shown that results strongly depart from intuitive models sometimes used in the literature. In particular, the polycrystal rheology is highly influenced by the poorly known hard slip systems and/or diffusion related processes.
Micromechanical modeling of the viscoplastic behavior of multiphase Earth mantle polycrystals
Detrez, F.; Castelnau, O.; Bollinger, C.; Cordier, P.; Hilairet, N.; Merkel, S.; Raterron, P. C.
2011-12-01
The strongly anisotropic rheology of olivine and pyroxene single grains, associated to polycrystal microstructures, constitutes a key feature affecting the dynamics of the Earth's upper mantle. High pressure deformation experiments carried out on olivine single crystals under synchrotron radiation, together with estimations of lattice friction based on first-principle calculations, show a transition from easy [100] to easy [001] slips in olivine as pressure and temperature (thus depth) increases. Besides dislocation glide, diffusion related deformation mechanisms such as dislocation climb, diffusional creep, and grain boundary sliding cannot be completely ruled out. Since their behavior is poorly known, they are grouped into a single isotropic viscous component. We input these elementary deformation mechanisms into a mean-field homogenization scheme (second-order self-consistent scheme of Ponte-Castaneda). This model presents the advantage of accurately predicting the mechanical interaction between deforming grains, as attested by many comparisons with full-field modeling on various polycrystals and 2-phases composites. The model has been adapted for predicting the viscoplastic behavior of olivine and olivine-pyroxene polycrystalline aggregates. Results illustrating the respective activation of elementary deformation mechanisms, but also the effect on texture evolution along several flow paths representative for in situ conditions, will be presented. It is shown that results strongly depart from intuitive models sometimes used in the literature. In particular, the polycrystal rheology is highly influenced by the poorly known hard slip systems and/or diffusion related processes.
Universal Reconfiguration of (Hyper-)cubic Robots
Abel, Zachary; Kominers, Scott D.
2008-01-01
We study a simple reconfigurable robot model which has not been previously examined: cubic robots comprised of three-dimensional cubic modules which can slide across each other and rotate about each others' edges. We demonstrate that the cubic robot model is universal, i.e., that an n-module cubic robot can reconfigure itself into any specified n-module configuration. Additionally, we provide an algorithm that efficiently plans and executes cubic robot motion. Our results directly extend to a...
Morphosynthesis of cubic silver cages on monolithic activated carbon.
Wang, Fei; Zhao, Hong; Lai, Yijian; Liu, Siyu; Zhao, Binyuan; Ning, Yuesheng; Hu, Xiaobin
2013-11-14
Cubic silver cages were prepared on monolithic activated carbon (MAC) pre-absorbed with Cl(-), SO4(2-), or PO4(3-) anions. Silver insoluble salts served as templates for the morphosynthesis of silver cages. The silver ions were reduced by reductive functional groups on MAC micropores through a galvanic cell reaction mechanism.
Cubication of Conservative Nonlinear Oscillators
Belendez, Augusto; Alvarez, Mariela L.; Fernandez, Elena; Pascual, Immaculada
2009-01-01
A cubication procedure of the nonlinear differential equation for conservative nonlinear oscillators is analysed and discussed. This scheme is based on the Chebyshev series expansion of the restoring force, and this allows us to approximate the original nonlinear differential equation by a Duffing equation in which the coefficients for the linear…
Cryptographic Analysis in Cubic Time
DEFF Research Database (Denmark)
Nielson, Flemming; Nielson, Hanne Riis; Seidl, H.
2004-01-01
The spi-calculus is a variant of the polyadic pi-calculus that admits symmetric cryptography and that admits expressing communication protocols in a precise though still abstract way. This paper shows that context-independent control flow analysis can be calculated in cubic time despite the fact ...
The diagonalization of cubic matrices
Cocolicchio, D.; Viggiano, M.
2000-08-01
This paper is devoted to analysing the problem of the diagonalization of cubic matrices. We extend the familiar algebraic approach which is based on the Cardano formulae. We rewrite the complex roots of the associated resolvent secular equation in terms of transcendental functions and we derive the diagonalizing matrix.
Institute of Scientific and Technical Information of China (English)
杨强; 杨卫
2001-01-01
The authors proposed a plausible explanation for the deviation of experimental data for sub-micron polycrystals from the Hall-Petch relation by in troducing the configuration entropy. The present paper extends the previous two dimensional analysis to the three-dimensional case. The statistical distribution of dislocation lengths within a spherical grain and the bow-out of dislocations are con sidered. According to Ashby's model, analyses are pursued for the statistically stored dislocations and geometrically necessary dislocations, respectively. It is confirmed that the configuration entropy model can predict the abnormal Hall-Petch depen dence for grain sizes in the sub-micron range.
Red long lasting phosphorescence of Eu3+ doped BiOCl semiconducting polycrystals
Institute of Scientific and Technical Information of China (English)
周玉婷; 宋志国; 李永进; 刘群; 徐祖元; 胡锐; 张相周; 邱建备; 杨正文
2016-01-01
The exploration of novel long lasting red phosphors is still of importance due to expected commercial applications and scientific interests. In this work, we reported the red long lasting phosphorescence (LLP) from Eu3+ doped BiOCl semiconductor polycrystals. The LLP property of the red phosphor is relatively weak due to less trap density, but the excitation band of LLP stems from the energy gap transition of semiconductor, offering experimental evidence for energy transfer between BiOCl semiconductor and Eu3+ ions. Although the afterglow duration of Eu3+ doped BiOCl was short temporarily, this work may open a novel kind of red LLP phosphors.
Lobach, I.; Benediktovitch, A.
2016-07-01
The possibility of quantitative texture analysis by means of parametric x-ray radiation (PXR) from relativistic electrons with Lorentz factor γ > 50MeV in a polycrystal is considered theoretically. In the case of rather smooth orientation distribution function (ODF) and large detector (θD >> 1/γ) the universal relation between ODF and intensity distribution is presented. It is shown that if ODF is independent on one from Euler angles, then the texture is fully determined by angular intensity distribution. Application of the method to the simulated data shows the stability of the proposed algorithm.
Variational method of determining effective moduli of polycrystals with tetragonal symmetry
Meister, R.; Peselnick, L.
1966-01-01
Variational principles have been applied to aggregates of randomly oriented pure-phase polycrystals having tetragonal symmetry. The bounds of the effective elastic moduli obtained in this way show a substantial improvement over the bounds obtained by means of the Voigt and Reuss assumptions. The Hill average is found to be a good approximation in most cases when compared to the bounds found from the variational method. The new bounds reduce in their limits to the Voigt and Reuss values. ?? 1966 The American Institute of Physics.
Peselnick, L.; Meister, R.
1965-01-01
Variational principles of anisotropic elasticity have been applied to aggregates of randomly oriented pure-phase polycrystals having hexagonal symmetry and trigonal symmetry. The bounds of the effective elastic moduli obtained in this way show a considerable improvement over the bounds obtained by means of the Voigt and Reuss assumptions. The Hill average is found to be in most cases a good approximation when compared to the bounds found from the variational method. The new bounds reduce in their limits to the Voigt and Reuss values. ?? 1965 The American Institute of Physics.
Takasaki, Tomoaki; Kyoi, Daisuke; Kitamura, Naoyuki; Tanase, Shigeo; Sakai, Tetsuo
2007-12-27
The face-centered cubic (fcc) type magnesium-zirconium hydride (Mg0.82Zr0.18Hx) was synthesized by means of the ultrahigh pressure (UHP) technique, which could generate 8 GPa of hydrogen pressure. The differential scanning calorimeter (DSC) measurements indicated that the fcc phase exhibited reversible hydrogen releasing and restoring properties under 0.5 MPa of hydrogen pressure. On the pressure-composition isotherms, the released and restored hydrogen capacities were estimated to be 3 approximately 3.5 wt %. The Rietveld analysis for synchrotron X-ray diffraction (XRD) data showed that the fcc phase had around 70 wt % mass fraction and was preserved without decomposition during hydrogen releasing and restoring cycles.
Cubication of conservative nonlinear oscillators
Energy Technology Data Exchange (ETDEWEB)
Belendez, Augusto; Alvarez, Mariela L [Departamento de Fisica, Ingenieria de Sistemas y Teoria de la Senal, Universidad de Alicante, Apartado 99, E-03080 Alicante (Spain); Fernandez, Elena; Pascual, Inmaculada [Departamento de Optica, FarmacologIa y Anatomia, Universidad de Alicante, Apartado 99, E-03080 Alicante (Spain)], E-mail: a.belendez@ua.es
2009-09-15
A cubication procedure of the nonlinear differential equation for conservative nonlinear oscillators is analysed and discussed. This scheme is based on the Chebyshev series expansion of the restoring force, and this allows us to approximate the original nonlinear differential equation by a Duffing equation in which the coefficients for the linear and cubic terms depend on the initial amplitude, A, while in a Taylor expansion of the restoring force these coefficients are independent of A. The replacement of the original nonlinear equation by an approximate Duffing equation allows us to obtain an approximate frequency-amplitude relation as a function of the complete elliptic integral of the first kind. Some conservative nonlinear oscillators are analysed to illustrate the usefulness and effectiveness of this scheme.
Cubic Matrix, Nambu Mechanics and Beyond
Kawamura, Y
2002-01-01
We propose a generalization of cubic matrix mechanics by introducing a canonical triplet and study its relation to Nambu mechanics. The generalized cubic matrix mechanics we consider can be interpreted as a “quantum” generalization of Nambu mechanics.
Cubical sets and the topological topos
DEFF Research Database (Denmark)
Spitters, Bas
2016-01-01
Coquand's cubical set model for homotopy type theory provides the basis for a computational interpretation of the univalence axiom and some higher inductive types, as implemented in the cubical proof assistant. This paper contributes to the understanding of this model. We make three contributions...... show that it can also be a target for cubical realization by showing that Coquand's cubical sets classify the geometric theory of flat distributive lattices. As a side result, we obtain a simplicial realization of a cubical set. 2. Using the internal `interval' in the topos of cubical sets, we...... construct a Moore path model of identity types. 3. We construct a premodel structure internally in the cubical type theory and hence on the fibrant objects in cubical sets....
Ibbotson, Matthew Gianni Equi
In an effort to measure the electrical grain boundary characteristics of fully dense (˜99%) cubic Li 7-3xAlxLa3Zr 2O12 (x = 0.05 - 0.3), small grain size samples of 1 - 2mum were made using the Spark Plasma Sintering (SPS) method. The large internal interfacial area of SPS samples increased the grain boundary contribution to the total resistance to separate typically overlapping bulk and grain boundary impedance responses, supporting grain boundary conductivity (sigma GB) measurements. sigmaGBwas on average two orders of magnitude lower than the bulk conductivity (sigmabulk), indicating the grain boundaries of this material are resistive to Li+ transport, despite literature reports of low grain boundary resistance. sigmaGB = 3.8x10-7 +/- 11%, 7.9x10-7 +/- 11%, and 4.8x10-7 +/- 27% S/cm at 250C with corresponding EaGB = 0.44 +/- 3%, 0.49 +/- 4%, 0.46 +/- 2% eV, for 5, 20, and 30mol%Al 3+ LLZO, respectively. The electrical grain boundary thickness (delta GB) calculated using the Brick Layer Model decreased monotonically with aluminum concentration (CAl3+) to indicate a possible space-charge effect on sigmaGB, and was deltaGB = 10.2 +/- 18% , 9.9 +/- 12% , 6.0 +/- 20% nm for 5, 20, and 30mol%Al LLZO, respectively. Non-linear behavior of sigmaGB with CAl3+ was discussed in terms of competing space-charge and impurity segregation effects that simultaneously influence lithium conduction in the electrical GB. Optimum sigmaGB and sigmabulk of 7.9x10-7 +/- 11% and 4.6x10-4 +/- 4% S/cm at 250C, respectively, were found to coincide at CAl3+ = 20mol%, the critical aluminum dopant concentration for cubic LLZO phase stability.
Numbers for reducible cubic scrolls
Directory of Open Access Journals (Sweden)
Israel Vainsencher
2004-12-01
Full Text Available We show how to compute the number of reducible cubic scrolls of codimension 2 in (math blackboard symbol Pn incident to the appropriate number of linear spaces.Mostramos como calcular o número de rolos cúbicos redutíveis de codimensão 2 em (math blackboard symbol Pn incidentes a espaços lineares apropriados.
Directory of Open Access Journals (Sweden)
M.M. Dardir
2014-03-01
Full Text Available Some hexanamide-mono and di-linoleniate esters were prepared by the reaction of linolenic acid and hexanamide (derived from the reaction of hexanoic acid and diethanolamine. The chemical structure for the newly prepared hexanamide-mono and di-linoleniate esters were elucidated using elemental analysis, (FTIR, H 1NMR and chemical ionization mass spectra (CI/Ms spectroscopic techniques. The results of the spectroscopic analysis indicated that they were prepared through the right method and they have high purity. The new prepared esters have high biodegradability and lower toxicity (environmentally friendly so they were evaluated as a synthetic-based mud (ester-based mud for oil-well drilling fluids. The evaluation included study of the rheological properties, filtration and thermal properties of the ester based-muds formulated with the newly prepared esters compared to the reference commercial synthetic-based mud.
A highly ordered cubic mesoporous silica/graphene nanocomposite
Lee, Chang-Wook; Roh, Kwang Chul; Kim, Kwang-Bum
2013-09-01
A highly ordered cubic mesoporous silica (KIT-6)/graphene nanocomposite and 2D KIT-6 nanoflakes were synthesized using a novel synthesis methodology. The non-ionic triblock copolymer, P123, played a dual role as a structure-directing agent in the formation of the cubic mesoporous structure and as a cross-linking agent between mesoporous silica and graphene. The prepared (KIT-6)/graphene nanocomposite could act as a template for the preparation of mesoporous material/graphene nanocomposites.A highly ordered cubic mesoporous silica (KIT-6)/graphene nanocomposite and 2D KIT-6 nanoflakes were synthesized using a novel synthesis methodology. The non-ionic triblock copolymer, P123, played a dual role as a structure-directing agent in the formation of the cubic mesoporous structure and as a cross-linking agent between mesoporous silica and graphene. The prepared (KIT-6)/graphene nanocomposite could act as a template for the preparation of mesoporous material/graphene nanocomposites. Electronic supplementary information (ESI) available: S1: TEM images of disordered mesoporous silica/graphene nanocomposite; S2: TEM images of KIT-6/GO nanocomposite; S3: Thermogravimetric analysis of KIT-6/GO and KG-400-700; S4: SEM and TEM images of KIT-6; S5: Low angle XRD, Raman spectra, N2 adsorption isotherms, pore size distribution and photographic images of the prepared samples; S6: TEM image and N2 adsorption isotherms of mesoporous carbon/graphene nanocomposite; S7: XPS C1s spectra of the prepared samples. See DOI: 10.1039/c3nr03108j
Energy Technology Data Exchange (ETDEWEB)
Palancher, H., E-mail: herve.palancher@cea.fr; Martin, G.; Fouet, J. [CEA, DEN, DEC, F-13108 Saint Paul lez Durance (France); Goudeau, P. [Institut Pprime, CNRS-Université de Poitiers–ENSMA, SP2MI, F-86360 Chasseneuil (France); Boulle, A. [Science des Procédés Céramiques et Traitements de Surface (SPCTS), CNRS UMR 7315, Centre Européen de la Céramique, 12 rue Atlantis, 87068 Limoges (France); Rieutord, F. [CEA, DSM, INAC, F-38054 Grenoble Cedex 9 (France); Favre-Nicolin, V. [Université Grenoble-Alpes, F-38041 Grenoble, France, Institut Universitaire de France, F-75005 Paris (France); Blanc, N. [Institut NEEL, CNRS-Univ Grenoble Alpes, F-38042 Grenoble (France); Onofri, C. [CEA, DEN, DEC, F-13108 Saint Paul lez Durance (France); CEMES, CNRS UPR 8011, 29 rue Jeanne Marvig, BP 94347, 31055 Toulouse Cedex 4 (France)
2016-01-18
The determination of the state of strain in implanted materials is a key issue in the study of their mechanical stability. Whereas this question is nowadays relatively easily solved in the case of single crystals, it remains a challenging task in the case of polycrystalline materials. In this paper, we take benefit of the intense and parallel beams provided by third generation synchrotron sources combined with a two-dimensional detection system to analyze individual grains in polycrystals, hence obtaining “single crystal-like” data. The feasibility of the approach is demonstrated with implanted UO{sub 2} polycrystals where the in-depth strain profile is extracted for individual grains using numerical simulations of the diffracted signal. The influence of the implantation dose is precisely analyzed for several diffracting planes and grains. This work suggests that, at low fluences, the development of strain is mainly due to ballistic effects with little effect from He ions, independently from the crystallographic orientation. At higher fluences, the evolution of the strain profiles suggests a partial and anisotropic plastic relaxation. With the present approach, robust and reliable structural information can be obtained, even from complex polycrystalline ceramic materials.
Energy Technology Data Exchange (ETDEWEB)
Berryman, J. G.
2012-03-01
While the well-known Voigt and Reuss (VR) bounds, and the Voigt-Reuss-Hill (VRH) elastic constant estimators for random polycrystals are all straightforwardly calculated once the elastic constants of anisotropic crystals are known, the Hashin-Shtrikman (HS) bounds and related self-consistent (SC) estimators for the same constants are, by comparison, more difficult to compute. Recent work has shown how to simplify (to some extent) these harder to compute HS bounds and SC estimators. An overview and analysis of a subsampling of these results is presented here with the main point being to show whether or not this extra work (i.e., in calculating both the HS bounds and the SC estimates) does provide added value since, in particular, the VRH estimators often do not fall within the HS bounds, while the SC estimators (for good reasons) have always been found to do so. The quantitative differences between the SC and the VRH estimators in the eight cases considered are often quite small however, being on the order of ±1%. These quantitative results hold true even though these polycrystal Voigt-Reuss-Hill estimators more typically (but not always) fall outside the Hashin-Shtrikman bounds, while the self-consistent estimators always fall inside (or on the boundaries of) these same bounds.
Cubic colloids : Synthesis, functionalization and applications
Castillo, S.I.R.
2015-01-01
This thesis is a study on cubic colloids: micron-sized cubic particles with rounded corners (cubic superballs). Owing to their shape, particle packing for cubes is more efficient than for spheres and results in fascinating phase and packing behavior. For our cubes, the particle volume fraction when
Cubic colloids : Synthesis, functionalization and applications
Castillo, S.I.R.
2015-01-01
This thesis is a study on cubic colloids: micron-sized cubic particles with rounded corners (cubic superballs). Owing to their shape, particle packing for cubes is more efficient than for spheres and results in fascinating phase and packing behavior. For our cubes, the particle volume fraction when
Solving Cubic Equations by Polynomial Decomposition
Kulkarni, Raghavendra G.
2011-01-01
Several mathematicians struggled to solve cubic equations, and in 1515 Scipione del Ferro reportedly solved the cubic while participating in a local mathematical contest, but did not bother to publish his method. Then it was Cardano (1539) who first published the solution to the general cubic equation in his book "The Great Art, or, The Rules of…
Cubic Icosahedra? A Problem in Assigning Symmetry
Lloyd, D. R.
2010-01-01
There is a standard convention that the icosahedral groups are classified separately from the cubic groups, but these two symmetry types have been conflated as "cubic" in some chemistry textbooks. In this note, the connection between cubic and icosahedral symmetries is examined, using a simple pictorial model. It is shown that octahedral and…
Cubic metaplectic forms and theta functions
Proskurin, Nikolai
1998-01-01
The book is an introduction to the theory of cubic metaplectic forms on the 3-dimensional hyperbolic space and the author's research on cubic metaplectic forms on special linear and symplectic groups of rank 2. The topics include: Kubota and Bass-Milnor-Serre homomorphisms, cubic metaplectic Eisenstein series, cubic theta functions, Whittaker functions. A special method is developed and applied to find Fourier coefficients of the Eisenstein series and cubic theta functions. The book is intended for readers, with beginning graduate-level background, interested in further research in the theory of metaplectic forms and in possible applications.
DEFF Research Database (Denmark)
Rodek, L.; Knudsen, E.; Poulsen, H.F.;
2005-01-01
The determination of crystalline structures is a demanding and fundamental task of crystallography. This paper offers a new approach for rendering a 2D grain map of a polycrystal based on an orientation map reconstructed from X-ray diffraction patterns. The orientation map is produced by a Bayesian...
Weighted cubic and biharmonic splines
Kvasov, Boris; Kim, Tae-Wan
2017-01-01
In this paper we discuss the design of algorithms for interpolating discrete data by using weighted cubic and biharmonic splines in such a way that the monotonicity and convexity of the data are preserved. We formulate the problem as a differential multipoint boundary value problem and consider its finite-difference approximation. Two algorithms for automatic selection of shape control parameters (weights) are presented. For weighted biharmonic splines the resulting system of linear equations can be efficiently solved by combining Gaussian elimination with successive over-relaxation method or finite-difference schemes in fractional steps. We consider basic computational aspects and illustrate main features of this original approach.
Verma, Purnima; Ahuja, Munish
2016-10-01
The purpose of this study was to investigate the potential of cubic liquid crystalline nanoparticles for ocular delivery of tropicamide. Ultrasound-assisted fragmentation of cubic liquid crystalline bulk phases resulted in cubic liquid crystalline nanoparticles employing Pluronic F127 as dispersant. The effects of process variables such as sonication time, sonication amplitude, sonication depth, and pre-mixing time on particle size and polydispersity index was investigated using central composite design. The morphology of tropicamide-loaded nanoparticles was found to be nearly cubical in shape by transmission electron microscopy observation. Further, small angle X-ray scattering experiment confirmed the presence of D and P phase cubic structures in coexistence. The optimized tropicamide-loaded cubic nanoparticles showed in vitro corneal permeation of tropicamide across isolated porcine cornea comparable to its commercial preparation, Tropicacyl®. Ocular tolerance was evaluated by Hen's egg-chorioallantoic membrane test and histological studies. The results of in vivo mydriatic response study demonstrated a remarkably higher area under mydriatic response curve (AUC0→1440 min) values of cubic nanoparticles over Tropicacyl® indicating better therapeutic value of cubic nanoparticles. Furthermore, tropicamide-loaded cubic nanoparticles exhibited prolonged mydriatic effect on rabbits as compared to commercial conventional aqueous ophthalmic solution.
Transparent polycrystalline cubic silicon nitride
Nishiyama, Norimasa; Ishikawa, Ryo; Ohfuji, Hiroaki; Marquardt, Hauke; Kurnosov, Alexander; Taniguchi, Takashi; Kim, Byung-Nam; Yoshida, Hidehiro; Masuno, Atsunobu; Bednarcik, Jozef; Kulik, Eleonora; Ikuhara, Yuichi; Wakai, Fumihiro; Irifune, Tetsuo
2017-01-01
Glasses and single crystals have traditionally been used as optical windows. Recently, there has been a high demand for harder and tougher optical windows that are able to endure severe conditions. Transparent polycrystalline ceramics can fulfill this demand because of their superior mechanical properties. It is known that polycrystalline ceramics with a spinel structure in compositions of MgAl2O4 and aluminum oxynitride (γ-AlON) show high optical transparency. Here we report the synthesis of the hardest transparent spinel ceramic, i.e. polycrystalline cubic silicon nitride (c-Si3N4). This material shows an intrinsic optical transparency over a wide range of wavelengths below its band-gap energy (258 nm) and is categorized as one of the third hardest materials next to diamond and cubic boron nitride (cBN). Since the high temperature metastability of c-Si3N4 in air is superior to those of diamond and cBN, the transparent c-Si3N4 ceramic can potentially be used as a window under extremely severe conditions. PMID:28303948
Bicontinuous cubic liquid crystalline nanoparticles for oral delivery of Doxorubicin
DEFF Research Database (Denmark)
Swarnakar, Nitin K; Thanki, Kaushik; Jain, Sanyog
2014-01-01
PURPOSE: The present study explores the potential of bicontinous cubic liquid crystalline nanoparticles (LCNPs) for improving therapeutic potential of doxorubicin. METHODS: Phytantriol based Dox-LCNPs were prepared using hydrotrope method, optimized for various formulation components, process...... variables and lyophilized. Structural elucidation of the reconstituted formulation was performed using HR-TEM and SAXS analysis. The developed formulation was subjected to exhaustive cell culture experiments for delivery potential (Caco-2 cells) and efficacy (MCF-7 cells). Finally, in vivo pharmacokinetics...
Force-Field Derivation and Atomistic Simulation of HMX/Graphite Interface and Polycrystal Systems
Institute of Scientific and Technical Information of China (English)
龙瑶; 刘永刚; 聂福德; 陈军
2012-01-01
Interface is the key issue to understand the performance of composite materials. In this work, we study the interface between octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine （HMX） and graphite, try to find out its contribution to mixture explosives. The work starts from the force-field derivation. We get ab initio based pair potentials across the interface, and then use them to study the interface structural and mechanical properties. A series of large scale molecular dynamics simulations are performed. The structure evolution, energy variation and elastic/plastic transformation of interface and polycrystal systems are calculated. The desensitizing mechanism of graphite to HMX is discussed.
Evaluating grain size in polycrystals with rough surfaces by corrected ultrasonic attenuation.
Li, Xiongbing; Han, Xiaoqin; Arguelles, Andrea P; Song, Yongfeng; Hu, Hongwei
2017-02-27
Surface roughness of a sample has a great effect on the calculated grain size when measurements are based on ultrasonic attenuation. Combining modified transmission and reflection coefficients at the rough interface with a Multi-Gaussian beam model of the transducer, a comprehensive correction scheme for the attenuation coefficient is developed. An approximate inverse model of the calculated attenuation, based on Weaver's diffuse scattering theory, is established to evaluate grain size in polycrystals. The experimental results showed that for samples with varying surface roughness and matching microstructures, the fluctuation of evaluated average grain size was ±1.17μm. For polished samples with different microstructures, the relative errors to optical microscopy were no more than ±3.61%. The presented method provides an effective nondestructive tool for evaluating the grain size in metals with rough surfaces.
Heterogeneous grain-scale response in ferroic polycrystals under electric field
DEFF Research Database (Denmark)
Daniels, John E.; Majkut, Marta; Cao, Qingua
2016-01-01
-ray diffraction (3D-XRD) is used to resolve the non-180° ferroelectric domain switching strain components of 191 grains from the bulk of a polycrystalline electro-ceramic that has undergone an electric-field-induced phase transformation. It is found that while the orientation of a given grain relative...... to the field direction has a significant influence on the phase and resultant domain texture, there are large deviations from the average behaviour at the grain scale. It is suggested that these deviations arise from local strain and electric field neighbourhoods being highly heterogeneous within the bulk...... polycrystal. Additionally, the minimisation of electrostatic potentials at the grain boundaries due to interacting ferroelectric domains must also be considered. It is found that the local grain-scale deviations average out over approximately 10–20 grains. These results provide unique insight into the grain-scale...
Constitutive modeling of strain rate effects in nanocrystalline and ultrafine grained polycrystals
Gurses, Ercan
2011-05-01
We present a variational two-phase constitutive model capable of capturing the enhanced rate sensitivity in nanocrystalline (nc) and ultrafine-grained (ufg) fcc metals. The nc/ufg-material consists of a grain interior phase and a grain boundary affected zone (GBAZ). The behavior of the GBAZ is described by a rate-dependent isotropic porous plasticity model, whereas a rate-independent crystal-plasticity model which accounts for the transition from partial dislocation to full dislocation mediated plasticity is employed for the grain interior. The scale bridging from a single grain to a polycrystal is done by a Taylor-type homogenization. It is shown that the enhanced rate sensitivity caused by the grain size refinement is successfully captured by the proposed model. © 2011 Elsevier Ltd. All rights reserved.
CVD-grown Fe2+:ZnSe polycrystals for laser applications
Firsov, K. N.; Gavrishchuk, E. M.; Ikonnikov, V. B.; Kazantsev, S. Yu; Kononov, I. G.; Rodin, S. A.; Savin, D. V.; Sirotkin, A. A.; Timofeeva, N. A.
2017-05-01
A technique for growing bulk zinc selenide polycrystals, doped with iron ions, by chemical vapor deposition (CVD), has been developed. It has been shown that iron is embedded in the crystal lattice of deposited zinc selenide in the optically active state of Fe2+. To improve the optical quality, the grown material was subjected to postgrowth hot isostatic pressing (HIP) treatment. It was experimentally demonstrated that the synthesised bulk crystals can be used as the active media of Fe2+:ZnSe lasers and as the passive Q-switches for three-micron lasers. The letter goes on to discuss the prospect of extending the proposed method to the synthesis of zinc sulphide doped with iron ions.
Energy Technology Data Exchange (ETDEWEB)
Lebensohn, Ricardo A [Los Alamos National Laboratory; Montagnat, Maurine [LGGE (FRANCE); Mansuy, Philippe [MICHELIN (FRANCE); Duval, Paul [LGGE (FRANCE); Philip, A [LGGE (FRANCE)
2008-01-01
A full-field formulation based on Fast Fourier Transforms (FFT) has been adapted and used to predict the micromechanical fields that develop in columnar Ih ice polycrystals deforming in compression by dislocation creep. The predicted intragranular mechanical fields are in qualitative good agreement with experimental observations, in particular those involving the formation of shear and kink bands. These localization bands are associated with the large internal stresses that develop during creep in such anisotropic material, and their location, intensity, morphology and extension are found to depend strongly on the crystallographic orientation of the grains and on their interaction with neighbor crystals. The predictions of the model are also discussed in relation with the deformation of columnar sea and lake ice, and with the mechanical behavior of granular ice of glaciers and polar ice sheets, as well.
Mechanical behaviour near grain boundaries of He-implanted UO2 ceramic polycrystals
Ibrahim, M.; Castelier, É.; Palancher, H.; Bornert, M.; Caré, S.; Micha, J.-S.
2017-01-01
For studying the micromechanical behaviour of UO2 and characterising the intergranular interaction, polycrystals are implanted with helium ions, inducing strains in a thin surface layer. Laue X-ray micro-diffraction is used to measure the strain field in this implanted layer with a spatial resolution of about 1 μm. It allows a 2D mapping of the strain field in a dozen of grains. These measurements show that the induced strain depends mainly on the crystal orientation, and can be evaluated by a semi-analytical mechanical model. A mechanical interaction of the neighbouring grains has also been evidenced near the grain boundaries, which has been well reproduced by a finite element model. This interaction is shown to increase with the implantation energy (i.e. the implantation depth): it can be neglected at low implantation energy (60 keV), but not at higher energy (500 keV).
Energy Technology Data Exchange (ETDEWEB)
Berryman, J.G.
2007-10-02
Some arguments of Bristow (1960) concerning the effects of cracks on elastic and transport (i.e., electrical or thermal conduction) properties of cold-worked metals are reexamined. The discussion is posed in terms of a modern understanding of bounds and estimates for physical properties of polycrystals--in contrast to Bristow's approach using simple mixture theory. One type of specialized result emphasized here is the cross-property estimates and bounds that can be obtained using the methods presented. Our results ultimately agree with those of Bristow, i.e., confirming that microcracking is not likely to be the main cause of the observed elastic behavior of cold-worked metals. However, it also becomes clear that the mixture theory approach to the analysis is too simple and that crack-crack interactions are necessary for proper quantitative study of Bristow's problem.
Saether, Erik; Glaessgen, Edward H.
2009-01-01
Atomistic simulations of intergranular fracture have indicated that grain-scale crack growth in polycrystalline metals can be direction dependent. At these material length scales, the atomic environment greatly influences the nature of intergranular crack propagation, through either brittle or ductile mechanisms, that are a function of adjacent grain orientation and direction of crack propagation. Methods have been developed to obtain cohesive zone models (CZM) directly from molecular dynamics simulations. These CZMs may be incorporated into decohesion finite element formulations to simulate fracture at larger length scales. A new directional decohesion element is presented that calculates the direction of Mode I opening and incorporates a material criterion for dislocation emission based on the local crystallographic environment to automatically select the CZM that best represents crack growth. The simulation of fracture in 2-D and 3-D aluminum polycrystals is used to illustrate the effect of parameterized CZMs and the effectiveness of directional decohesion finite elements.
Maurel, Agnès; Mercier, Jean-François; Montagnat, Maurine
2016-12-01
Crystallographic texture (or fabric) evolution with depth along ice cores can be evaluated using borehole sonic logging measurements. These measurements provide the velocities of elastic waves that depend on the ice polycrystal anisotropy, and they can further be related to the ice texture. To do so, elastic velocities need to be inverted from a modeling approach that relate elastic velocities to ice texture. So far, two different approaches can be found. A classical model is based on the effective medium theory; the velocities are derived from elastic wave propagation in a homogeneous medium characterized by an average elasticity tensor. Alternatively, a velocity averaging approach was used in the glaciology community that averages the velocities from a given population of single crystals with different orientations. In this paper, we show that the velocity averaging method is erroneous in the present context. This is demonstrated for the case of waves propagating along the clustering direction of a highly textured polycrystal, characterized by crystallographic c axes oriented along a single maximum (cluster). In this case, two different shear wave velocities are obtained while a unique velocity is theoretically expected. While making use of this velocity averaging method, reference work by Bennett (1968) does not end with such an unphysical result. We show that this is due to the use of erroneous expressions for the shear wave velocities in a single crystal, as the starting point of the averaging process. Because of the weak elastic anisotropy of ice single crystal, the inversion of the measured velocities requires accurate modeling approaches. We demonstrate here that the inversion method based on the effective medium theory provides physically based results and should therefore be favored.
Energy Technology Data Exchange (ETDEWEB)
Clausen, B.
1997-09-01
The deformation of polycrystals are modelled using three micron mechanic models; the Taylor model, the Sachs model and Hutchinson`s self-consistent (SC) model. The predictions of the rigid plastic Taylor and Sachs models are compared with the predictions of the SC model. As expected, the results of the SC model is about half-way between the upper- and lower-bound models. The influence of the elastic anisotropy is investigated by comparing the SC predictions for aluminium, copper and a hypothetical material (Hybrid) with the elastic anisotropy of copper and the Young`s modulus and hardening behaviour of aluminium. It is concluded that the effect of the elastic anisotropy is limited to the very early stages of plasticity, as the deformation pattern is almost identical for the three materials at higher strains. The predictions of the three models are evaluated by neutron diffraction measurements of elastic lattice strains in grain sub-sets within the polycrystal. The two rigid plastic models do not include any material parameters and therefore the predictions of the SC model is more accurate and more detailed than the predictions of the Taylor and Sachs models. The SC model is used to determine the most suitable reflection for technological applications of neutron diffraction, where focus is on the volume average stress state in engineering components. To be able to successfully to convert the measured elastic lattice strains for a specific reflection into overall volume average stresses, there must be a linear relation between the lattice strain of the reflection and the overall stress. According to the model predictions the 311-reflection is the most suitable reflection as it shows the smallest deviations from linearity and thereby also the smallest build-up of residual strains. The model predictions have pin pointed that the selection of the reflection is crucial for the validity of stresses calculated from the measured elastic lattice strains. (au) 14 tabs., 41
Tame Kernels of Pure Cubic Fields
Institute of Scientific and Technical Information of China (English)
Xiao Yun CHENG
2012-01-01
In this paper,we study the p-rank of the tame kernels of pure cubic fields.In particular,we prove that for a fixed positive integer m,there exist infinitely many pure cubic fields whose 3-rank of the tame kernel equal to m.As an application,we determine the 3-rank of their tame kernels for some special pure cubic fields.
Two-dimensional cubic convolution.
Reichenbach, Stephen E; Geng, Frank
2003-01-01
The paper develops two-dimensional (2D), nonseparable, piecewise cubic convolution (PCC) for image interpolation. Traditionally, PCC has been implemented based on a one-dimensional (1D) derivation with a separable generalization to two dimensions. However, typical scenes and imaging systems are not separable, so the traditional approach is suboptimal. We develop a closed-form derivation for a two-parameter, 2D PCC kernel with support [-2,2] x [-2,2] that is constrained for continuity, smoothness, symmetry, and flat-field response. Our analyses, using several image models, including Markov random fields, demonstrate that the 2D PCC yields small improvements in interpolation fidelity over the traditional, separable approach. The constraints on the derivation can be relaxed to provide greater flexibility and performance.
Cubical local partial orders on cubically subdivided spaces - Existence and construction
DEFF Research Database (Denmark)
Fajstrup, Lisbeth
2006-01-01
The geometric models of higher dimensional automata (HDA) and Dijkstra's PV-model are cubically subdivided topological spaces with a local partial order. If a cubicalization of a topological space is free of immersed cubic Möbius bands, then there are consistent choices of direction in all cubes...
Cubical local partial orders on cubically subdivided spaces - existence and construction
DEFF Research Database (Denmark)
Fajstrup, Lisbeth
The geometric models of Higher Dimensional Automata and Dijkstra's PV-model are cubically subdivided topological spaces with a local partial order. If a cubicalization of a topological space is free of immersed cubic Möbius bands, then there are consistent choices of direction in all cubes...
CLASSIFICATION OF CUBIC PARAMETERIZED HOMOGENEOUS VECTOR FIELDS
Institute of Scientific and Technical Information of China (English)
Karnal H.Yasir; TANG Yun
2002-01-01
In this paper the cubic homogeneous parameterized vector fields are studied.The classification of the phase portrait near the critical point is presented. This classification is an extension of the result given by Takens to the cubic homogeneous parameterized vector fields with six parameters.
CLASSIFICATION OF CUBIC PARAMETERIZED HOMOGENEOUS VECTOR FIELDS
Institute of Scientific and Technical Information of China (English)
KamalH.Yasir; TNAGYun
2002-01-01
In this paper the cubic homogeneous parameterized vector fields are studied.The classification of the phase portrait near the critical point is presented.This classification is an extension of the result given by takens to the cubic homogeneous parameterized vector fields with six parameters.
Institute of Scientific and Technical Information of China (English)
Liqing CHEN; Naoyuki Kanetake
2005-01-01
Ingot metallurgy (IM) aluminum has long been the subject and attracted the attention of many metallurgists and textural researchers of materials. Due to the introduction of large amounts of ex situ interfaces, however, the textures in powder metallurgy (PM) processed aluminum has been rarely reported. In this article, a pure aluminum plate was prepared via PM route. The starting billet was first produced with uni-axially cold compaction and flat hot-extrusion and then followed by cold rolling processes. The hot-extruded and cold rolling deformation textures of the pure PM aluminum at 50%, 80% and 90% cold rolling reductions were studied by orientation distribution functions (ODFs) analysis. The finite element polycrystal model (FEPM) was finally utilized to simulate the cold rolling textural evolution at various stages of cold rolling. In FEPM simulation, the initial hot-extruded textures were taken into account as inputs. The results showed that typical β-fiber texture formed in pure PM aluminum with the cold rolling reduction increased till 80%, and there was not much change after excessive cold rolling deformation.Homogeneous slip is not the only deformation mode in PM processed pure aluminum plate at over 80% cold rolling reduction. The experimental results were qualitatively in good agreement with the simulated ones.
Energy Technology Data Exchange (ETDEWEB)
Ponce, C A [Departamento de Fisica, Facultad de Ciencias Exactas, y Naturales y Agrimensura, UNNE, Campus Universitario, Avenida Libertad 5600, CP 3400, Corrientes (Argentina); Casali, R A [Departamento de Fisica, Facultad de Ciencias Exactas, y Naturales y Agrimensura, UNNE, Campus Universitario, Avenida Libertad 5600, CP 3400, Corrientes (Argentina); Caravaca, M A [Departamento de Fisico, Quimica, Facultad de Ingenieria, UNNE, Avenida Las Heras 727, CP 3500, Resistencia (Argentina)
2008-01-30
By means of the ab initio all-electron new full-potential linear-muffin-tin orbitals method, calculations were made for elastic constants C{sub 11}, C{sub 12} and C{sub 44} for Si, ZrO{sub 2} and HfO{sub 2} in their cubic phase, and constants C{sub 11}, C{sub 22}, C{sub 33}, C{sub 12}, C{sub 13}, C{sub 23}, C{sub 44}, C{sub 55} and C{sub 66} for HfO{sub 2} in its orthorhombic phase. Using the Voigt and Reuss theory, estimations were made for polycrystals of their bulk, shear and Young moduli, and Poisson coefficients. The speed of elastic wave propagations and Debye temperatures were estimated for polycrystals built from Si and the above mentioned compounds. The semicore 4f{sup 14} electrons should be included in the valence set of Hf atom in this all-electron approach if accurate results for elastic properties under pressures are looked for.
Cubic III-nitrides: potential photonic materials
Onabe, K.; Sanorpim, S.; Kato, H.; Kakuda, M.; Nakamura, T.; Nakamura, K.; Kuboya, S.; Katayama, R.
2011-01-01
The growth and characterization of some cubic III-nitride films on suitable cubic substrates have been done, namely, c- GaN on GaAs by MOVPE, c-GaN and c-AlGaN on MgO by RF-MBE, and c-InN and c-InGaN (In-rich) on YSZ by RFMBE. This series of study has been much focused on the cubic-phase purity as dependent on the respective growth conditions and resulting electrical and optical properties. For c-GaN and c-InN films, a cubic-phase purity higher than 95% is attained in spite of the metastable nature of the cubic III-nitrides. However, for c-AlGaN and c-InGaN films, the cubic-phase purity is rapidly degraded with significant incorporation of the hexagonal phase through stacking faults on cubic {111} faces which may be exposed on the roughened growing or substrate surface. It has been shown that the electron mobilities in c-GaN and c-AlGaN films are much related to phase purity.
Cubic Curves, Finite Geometry and Cryptography
Bruen, A A; Wehlau, D L
2011-01-01
Some geometry on non-singular cubic curves, mainly over finite fields, is surveyed. Such a curve has 9,3,1 or 0 points of inflexion, and cubic curves are classified accordingly. The group structure and the possible numbers of rational points are also surveyed. A possible strengthening of the security of elliptic curve cryptography is proposed using a `shared secret' related to the group law. Cubic curves are also used in a new way to construct sets of points having various combinatorial and geometric properties that are of particular interest in finite Desarguesian planes.
Generalized Vaidya spacetime for cubic gravity
Ruan, Shan-Ming
2015-01-01
We present a kind of generalized Vaidya solutions of a new cubic gravity in five dimensions whose field equations in spherically spacetime are always second order like the Lovelock gravity. We also study the thermodynamics of its apparent horizon and get its entropy expression and generalized Misner-Sharp energy. Finally we present the first law and second law hold in this gravity. Although all the results are analogue to those in Lovelock gravity, we in fact introduce the contribution of new cubic term in five dimensions where cubic Lovelock term is just zero.
Cubical sets as a classifying topos
DEFF Research Database (Denmark)
Spitters, Bas
Coquand’s cubical set model for homotopy type theory provides the basis for a computational interpretation of the univalence axiom and some higher inductive types, as implemented in the cubical proof assistant. We show that the underlying cube category is the opposite of the Lawvere theory of De...... Morgan algebras. The topos of cubical sets itself classifies the theory of ‘free De Morgan algebras’. This provides us with a topos with an internal ‘interval’. Using this interval we construct a model of type theory following van den Berg and Garner. We are currently investigating the precise relation...
Kakehata, Masayuki; Yashiro, Hidehiko; Oyane, Ayako; Ito, Atsuo; Torizuka, Kenji
2016-03-01
Three-mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) is a fine engineering ceramic that offers high fracture resistance and flexural strength. Thus, it is often applied in mechanical components and medical implants. The surface roughness can be controlled to improve the device characters in some applications. Ultrashort pulse lasers can form laser-induced periodic surface structures (LIPSS) on 3Y-TZP, which have never been investigated in detail. Therefore, this paper reports the formation and characteristics of LIPSS formed on 3Y-TZP, focusing on the pulsewidth dependence. The LIPSS was formed by a Ti:sapphire chirped-pulse amplification system, which generates 810 nmcentered 80-fs pulses at a 570 Hz repetition rate. The measured ablation threshold peak fluence was ~1.5 J/cm2 and the LIPSS was formed at the peak fluence of 2.7-7.7 J/cm2. For linearly polarized pulses, the lines of the LIPSS were oriented parallel to the polarization direction, and their period was comparable to or larger than the center wavelength of the laser. These characteristics differ from the reported characteristics of LIPSS on metals and dielectrics. The pulsewidth dependence of the ablation and LIPSS was investigated for different pulsewidths and signs of chirp. Under the investigated fluence condition, the LIPSS period increased with increasing pulsewidth for both signs of chirp. Similar pulsewidth dependencies were observed for circularly polarized pulses.
Changes in X-ray photoelectron spectra of yttria-tetragonal zirconia polycrystal by ion sputtering
Energy Technology Data Exchange (ETDEWEB)
Watanabe, Eiko; Yoshinari, Masao [Tokyo Dental College, Oral Health Science Center, Tokyo, Chiyoda-ku (Japan)
2016-04-15
This paper reports changes in X-ray photoelectron spectroscopy spectra of yttria-tetragonal zirconia polycrystal (Y-TZP) brought about by Ar ion sputtering. The changes in the core-level spectra of Y-TZP suggest that preferential sputtering of oxygen occurred. A new peak was observed near 0 eV binding energy accompanied with changes in the core-level spectra by the sputtering. After 18 h in a high vacuum following the sputtering, the spectra changed by the sputtering were returned to their original shapes. In contrast, the color of Y-TZP was changed from white to pale brown by X-ray irradiation and was changed from pale brown to dark gray by ion sputtering. However, when the new peak near 0 eV decreased after 18 h, no color change was observed. Therefore, it is thought that the new peak was mainly derived from electrons trapped in various kinds of oxygen vacancies created by the sputtering in other than color centers. (orig.)
Wear behavior of tetragonal zirconia polycrystal versus titanium and titanium alloy
Energy Technology Data Exchange (ETDEWEB)
Kanbara, Tsunemichi; Yajima, Yasutomo [Department of Oral Implantology, Tokyo Dental College, 1-2-2 Masago, Mihama-ku, Chiba 261-8502 (Japan); Yoshinari, Masao, E-mail: yosinari@tdc.ac.jp [Division of Oral Implant Research, Oral Health Science Center, Tokyo Dental College, 1-2-2 Masago, Mihama-ku, Chiba 261-8502 (Japan)
2011-04-15
The aim of this study was to clarify the influence of tetragonal zirconia polycrystal (TZP) on the two-body wear behavior of titanium (Ti). Two-body wear tests were performed using TZP, two grades of cp-Ti or Ti alloy in distilled water, and the cross-sectional area of worn surfaces was measured to evaluate the wear behavior. In addition, the surface hardness and coefficient of friction were determined and an electron probe microanalysis performed to investigate the underlying mechanism of wear. The hardness of TZP was much greater than that of Ti. The coefficient of friction between Ti and Ti showed a higher value than the Ti/TZP combination. Ti was more susceptible to wear by both TZP and Ti than TZP, indicating that the mechanism of wear between TZP and Ti was abrasive wear, whereas that between Ti and Ti was adhesive wear. No remarkable difference in the amount of wear in Ti was observed between TZP and Ti as the opposite material, despite the hardness value of Ti being much smaller than that of TZP. (communication)
MOVING SCREW DISLOCATION IN CUBIC QUASICRYSTAL
Institute of Scientific and Technical Information of China (English)
ZHOU Wang-min; SONG Yu-hai
2005-01-01
The elasticity theory of the dislocation of cubic quasicrystals is developed.The governing equations of anti-plane elasticity dynamics problem of the quasicrystals were reduced to a solution of wave equations by introducing displacement functions,and the analytical expressions of displacements, stresses and energies induced by a moving screw dislocation in the cubic quasicrystalline and the velocity limit of the dislocation were obtained. These provide important information for studying the plastic deformation of the new solid material.
2-rational Cubic Spline Involving Tension Parameters
Indian Academy of Sciences (India)
M Shrivastava; J Joseph
2000-08-01
In the present paper, 1-piecewise rational cubic spline function involving tension parameters is considered which produces a monotonic interpolant to a given monotonic data set. It is observed that under certain conditions the interpolant preserves the convexity property of the data set. The existence and uniqueness of a 2-rational cubic spline interpolant are established. The error analysis of the spline interpolant is also given.
Semisymmetric Cubic Graphs of Order 162
Indian Academy of Sciences (India)
Mehdi Alaeiyan; Hamid A Tavallaee; B N Onagh
2010-02-01
An undirected graph without isolated vertices is said to be semisymmetric if its full automorphism group acts transitively on its edge set but not on its vertex set. In this paper, we inquire the existence of connected semisymmetric cubic graphs of order 162. It is shown that for every odd prime , there exists a semisymmetric cubic graph of order 162 and its structure is explicitly specified by giving the corresponding voltage rules generating the covering projections.
Cubical version of combinatorial differential forms
DEFF Research Database (Denmark)
Kock, Anders
2010-01-01
The theory of combinatorial differential forms is usually presented in simplicial terms. We present here a cubical version; it depends on the possibility of forming affine combinations of mutual neighbour points in a manifold, in the context of synthetic differential geometry.......The theory of combinatorial differential forms is usually presented in simplicial terms. We present here a cubical version; it depends on the possibility of forming affine combinations of mutual neighbour points in a manifold, in the context of synthetic differential geometry....
High-temperature plastic deformation of fine-grained Y-doped BaCeO{sub 3} polycrystals
Energy Technology Data Exchange (ETDEWEB)
Vaquero-Aguilar, C; Jimenez-Melendo, M [Departamento de Fisica de la Materia Condensada, Universidad de Sevilla. Aptdo. 1065. 41080 Sevilla (Spain); Real, C, E-mail: melendo@us.e [Instituto de Ciencia de Materiales de Sevilla, Centro Mixto CSIC-US, Av. Americo Vespucio 49. 41092 Sevilla (Spain)
2010-07-01
The high-temperature plastic deformation of BaCe{sub 0.95}Y{sub 0.05}O{sub 3-{delta}} polycrystals with average grain size of 0.50 {mu}m has been studied in compression between 1000 and 1250{sup 0}C in air at different initial strain rates. The stress-strain curves display yield drop at strains close to 5%, followed by steady state or strain-softening stages. Large ductilities were achieved at the higher temperatures, without appreciable changes in grain shape and size. Mechanical data and microstructural observations are consistent with a flow mechanism by grain boundary sliding.
Timofeev, I. S.; Burdonskiy, I. N.; Goltsov, A. Yu; Leonov, A. G.; Makarov, K. N.; Yufa, V. N.
2016-09-01
The paper presents the analysis of interaction of the high-power laser pulse with multicomponent polycrystal rocks. Experiments were completed on a laser facility “Saturn” with intensity of 1010-1013 W/cm2. Structural analysis of the materials from the spall crater and from the plasma flame show significant differences. The article demonstrates experimental results of the spall formation moment depending on the thickness of the radiated target. The scale of damage to aluminium 6 pm thick foil at the rare side of the target is illustrated when it is hit by the andesite fragments from a spall crater.
Interpolation by two-dimensional cubic convolution
Shi, Jiazheng; Reichenbach, Stephen E.
2003-08-01
This paper presents results of image interpolation with an improved method for two-dimensional cubic convolution. Convolution with a piecewise cubic is one of the most popular methods for image reconstruction, but the traditional approach uses a separable two-dimensional convolution kernel that is based on a one-dimensional derivation. The traditional, separable method is sub-optimal for the usual case of non-separable images. The improved method in this paper implements the most general non-separable, two-dimensional, piecewise-cubic interpolator with constraints for symmetry, continuity, and smoothness. The improved method of two-dimensional cubic convolution has three parameters that can be tuned to yield maximal fidelity for specific scene ensembles characterized by autocorrelation or power-spectrum. This paper illustrates examples for several scene models (a circular disk of parametric size, a square pulse with parametric rotation, and a Markov random field with parametric spatial detail) and actual images -- presenting the optimal parameters and the resulting fidelity for each model. In these examples, improved two-dimensional cubic convolution is superior to several other popular small-kernel interpolation methods.
Superhard BC(3) in cubic diamond structure.
Zhang, Miao; Liu, Hanyu; Li, Quan; Gao, Bo; Wang, Yanchao; Li, Hongdong; Chen, Changfeng; Ma, Yanming
2015-01-01
We solve the crystal structure of recently synthesized cubic BC(3) using an unbiased swarm structure search, which identifies a highly symmetric BC(3) phase in the cubic diamond structure (d-BC(3)) that contains a distinct B-B bonding network along the body diagonals of a large 64-atom unit cell. Simulated x-ray diffraction and Raman peaks of d-BC(3) are in excellent agreement with experimental data. Calculated stress-strain relations of d-BC(3) demonstrate its intrinsic superhard nature and reveal intriguing sequential bond-breaking modes that produce superior ductility and extended elasticity, which are unique among superhard solids. The present results establish the first boron carbide in the cubic diamond structure with remarkable properties, and these new findings also provide insights for exploring other covalent solids with complex bonding configurations.
Cubical Cohomology Ring of 3D Photographs
Gonzalez-Diaz, Rocio; Medrano, Belen; 10.1002/ima.20271
2011-01-01
Cohomology and cohomology ring of three-dimensional (3D) objects are topological invariants that characterize holes and their relations. Cohomology ring has been traditionally computed on simplicial complexes. Nevertheless, cubical complexes deal directly with the voxels in 3D images, no additional triangulation is necessary, facilitating efficient algorithms for the computation of topological invariants in the image context. In this paper, we present formulas to directly compute the cohomology ring of 3D cubical complexes without making use of any additional triangulation. Starting from a cubical complex $Q$ that represents a 3D binary-valued digital picture whose foreground has one connected component, we compute first the cohomological information on the boundary of the object, $\\partial Q$ by an incremental technique; then, using a face reduction algorithm, we compute it on the whole object; finally, applying the mentioned formulas, the cohomology ring is computed from such information.
Purely cubic action for string field theory
Horowitz, G. T.; Lykken, J.; Rohm, R.; Strominger, A.
1986-01-01
It is shown that Witten's (1986) open-bosonic-string field-theory action and a closed-string analog can be written as a purely cubic interaction term. The conventional form of the action arises by expansion around particular solutions of the classical equations of motion. The explicit background dependence of the conventional action via the Becchi-Rouet-Stora-Tyutin operator is eliminated in the cubic formulation. A closed-form expression is found for the full nonlinear gauge-transformation law.
Purely cubic action for string field theory
Horowitz, G. T.; Lykken, J.; Rohm, R.; Strominger, A.
1986-01-01
It is shown that Witten's (1986) open-bosonic-string field-theory action and a closed-string analog can be written as a purely cubic interaction term. The conventional form of the action arises by expansion around particular solutions of the classical equations of motion. The explicit background dependence of the conventional action via the Becchi-Rouet-Stora-Tyutin operator is eliminated in the cubic formulation. A closed-form expression is found for the full nonlinear gauge-transformation law.
Energy Technology Data Exchange (ETDEWEB)
Berryman, J G
2004-09-16
Peselnick, Meister, and Watt have developed rigorous methods for bounding elastic constants of random polycrystals based on the Hashin-Shtrikman variational principles. In particular, a fairly complex set of equations that amounts to an algorithm has been presented previously for finding the bounds on effective elastic moduli for polycrystals having hexagonal, trigonal, and tetragonal symmetries. The more analytical approach developed here, although based on the same ideas, results in a new set of compact formulas for all the cases considered. Once these formulas have been established, it is then straightforward to perform what could be considered an analytic continuation of the formulas (into the region of parameter space between the bounds) that can subsequently be used to provide self-consistent estimates for the elastic constants in all cases. These self-consistent estimates are easily shown (essentially by construction) to lie within the bounds for all the choices of crystal symmetry considered. Estimates obtained this way are quite comparable to those found by the Gubernatis and Krumhansl CPA (coherent potential approximation), but do not require any computations of scattering coefficients.
Mainprice, David; Lloyd, Geoffrey E.; Casey, Martin
1993-09-01
Individual orientation determination of quartz grains by electron channelling in principle gives the complete orientation. However, in routine analysis the noise level in electron channelling patterns (ECPs) does not permit the determination of handedness of a quartz grain in a polycrystal. In practice, all quartz grains are arbitrarily indexed as right-handed. Hence, Dauphiné twins can be identified, but not Brazil twins. This practice also means that only the centrosymmetric petrophysical properties can be determined from texture measurements. These include most geologically relevant properties (e.g. thermal conductivity, thermal expansion and elasticity). However, other properties (e.g. piezoelectricity) which are not centrosymmetric cannot be calculated from such texture measurements. Some texture-forming processes (e.g. dislocation glide) can also be considered to be centrosymmetric in quartz, whereas others (e.g. grain boundary migration) may not be. The method of quantitative texture analysis from individual measurements is briefly recalled. As an example, 382 grains from Tongue quartzite are used to illustrate the advantages of texture analysis from ECPs. The orientation distribution function (ODF) is calculated from ECPs and X-ray pole figures of the same sample. The agreement is found to be good between the two methods, proving that ECPs can be used for quantitative analysis. The methods used in local texture analysis and the definitions of the various misorientation distribution functions (MODFs) are given. Data collected from a traverse of a quartzo-feldspathic shear zone in Lewisian gneiss (Torridon 'quartzite') are used to illustrate local texture analysis. Examples from a region of shear strain of about one are given of core and mantle subgrains and Dauphiné twins. Dispersion trails of the crystallographic axes within a single grain show an apparent rotation about the intermediate structural axis Y. Detailed analysis of the subgrain misorientation
DEFICIENT CUBIC SPLINES WITH AVERAGE SLOPE MATCHING
Institute of Scientific and Technical Information of China (English)
V. B. Das; A. Kumar
2005-01-01
We obtain a deficient cubic spline function which matches the functions with certain area matching over a greater mesh intervals, and also provides a greater flexibility in replacing area matching as interpolation. We also study their convergence properties to the interpolating functions.
Counting rational points on cubic curves
Institute of Scientific and Technical Information of China (English)
HEATH-BROWN; Roger; TESTA; Damiano
2010-01-01
We prove upper bounds for the number of rational points on non-singular cubic curves defined over the rationals.The bounds are uniform in the curve and involve the rank of the corresponding Jacobian.The method used in the proof is a combination of the "determinant method" with an m-descent on the curve.
CONSTRAINED RATIONAL CUBIC SPLINE AND ITS APPLICATION
Institute of Scientific and Technical Information of China (English)
Qi Duan; Huan-ling Zhang; Xiang Lai; Nan Xie; Fu-hua (Frank) Cheng
2001-01-01
In this paper, a kind of rational cubic interpolation functionwith linear denominator is constructed. The constrained interpolation with constraint on shape of the interpolating curves and on the second-order derivative of the interpolating function is studied by using this interpolation, and as the consequent result, the convex interpolation conditions have been derived.
Anisotropy of a cubic ferromagnet at criticality
Kudlis, A.; Sokolov, A. I.
2016-10-01
Critical fluctuations change the effective anisotropy of cubic ferromagnet near the Curie point. If the crystal undergoes phase transition into orthorhombic phase and the initial anisotropy is not too strong, reduced anisotropy of nonlinear susceptibility acquires at Tc the universal value δ4*=2/v* 3 (u*+v*) where u* and v* are coordinates of the cubic fixed point on the flow diagram of renormalization group equations. In the paper, the critical value of the reduced anisotropy is estimated within the pseudo-ɛ expansion approach. The six-loop pseudo-ɛ expansions for u*, v*, and δ4* are derived for the arbitrary spin dimensionality n . For cubic crystals (n =3 ) higher-order coefficients of the pseudo-ɛ expansions obtained turn out to be so small that use of simple Padé approximants yields reliable numerical results. Padé resummation of the pseudo-ɛ series for u*, v*, and δ4* leads to the estimate δ4*=0.079 ±0.006 , indicating that detection of the anisotropic critical behavior of cubic ferromagnets in physical and computer experiments is certainly possible.
Binomial Squares in Pure Cubic Number Fields
Lemmermeyer, Franz
2011-01-01
Let K = Q(\\omega) with \\omega^3 = m be a pure cubic number field. We show that the elements\\alpha \\in K^\\times whose squares have the form a - \\omega form a group isomorphic to the group of rational points on the elliptic curve E_m: y^2= x^3 - m.
The cactus rank of cubic forms
Bernardi, Alessandra
2011-01-01
We prove that the smallest degree of an apolar 0-dimensional scheme to a general cubic form in $n+1$ variables is at most $2n+2$, when $n\\geq 8$, and therefore smaller than the rank of the form. When n=8 we show that the bound is sharp, i.e. the smallest degree of an apolar subscheme is 18.
Ytterbium: Transition at High Pressure from Face-Centered Cubic to Body-Centered Cubic Structure.
Hall, H T; Barnett, J D; Merrill, L
1963-01-11
Pressure of 40,000 atmospheres at 25 degrees C induces a phase transformation in ytterbium metal; the face-centered cubic structure changes to body-centered cubic. The radius of the atom changes from 1.82 to 1.75 A. At the same time the atom's volume decreases by 11 percent and the volume, observed macroscopically, decreases 3.2 percent.
Directory of Open Access Journals (Sweden)
Xingxing Wang
2011-01-01
Full Text Available Cubic copper hexacyanoferrate (CuHCF nanoparticles prepared via electrolytic deposition are presented with their morphology and crystalline structure characterized with SEM and XRD. The advantage of this methodology is that it allows the fabrication of uniform cubic nanoparticles with permeable structures onto the desired underlying electrode substrate. It was observed that the CuHCF film acts as a permeable membrane for cations such as K+, Na+, Li+, and NH4+ with a selection order of K+> Li+>NH4+> Na+. Furthermore, the analytical utility of these cubic-like CuHCF morphologies supported on a glassy carbon electrode was evaluated towards the electrochemical oxidation of hydrazine which was found to exhibit a linear response over the range 66 M to 17 mM with a detection limit corresponding to 16.5 M.
Directory of Open Access Journals (Sweden)
Dian L
2013-02-01
Full Text Available Linghui Dian,1,2,* Zhiwen Yang,3,* Feng Li,1 Zhouhua Wang,1 Xin Pan,1 Xinsheng Peng,2 Xintian Huang,1 Zhefei Guo,1 Guilan Quan,1 Xuan Shi,1 Bao Chen,1 Ge Li,4 Chuanbin Wu1,41School of Pharmaceutical Sciences, Sun Yat-Sen University, University Town, Guangzhou, People’s Republic of China; 2School of Pharmaceutical Sciences, Guangdong Medical College, Dongguan, People’s Republic of China; 3Department of Gastroenterology, Songjiang Branch of the Affiliated First People’s Hospital of Shanghai Jiaotong University, Shanghai, People’s Republic of China; 4Guangdong Research Center for Drug Delivery Systems, Guangzhou, People’s Republic of China*These authors contributed equally to this workAbstract: In order to improve the oral bioavailability of ibuprofen, ibuprofen-loaded cubic nanoparticles were prepared as a delivery system for aqueous formulations. The cubic inner structure was verified by cryogenic transmission electron microscopy. With an encapsulation efficiency greater than 85%, the ibuprofen-loaded cubic nanoparticles had a narrow size distribution around a mean size of 238 nm. Differential scanning calorimetry and X-ray diffraction determined that ibuprofen was in an amorphous and molecular form within the lipid matrix. The in vitro release of ibuprofen from cubic nanoparticles was greater than 80% at 24 hours, showing sustained characteristics. The pharmacokinetic study in beagle dogs showed improved absorption of ibuprofen from cubic nanoparticles compared to that of pure ibuprofen, with evidence of a longer half-life and a relative oral bioavailability of 222% (P < 0.05. The ibuprofen-loaded cubic nanoparticles provide a promising carrier candidate with an efficient drug delivery for therapeutic treatment.Keywords: ibuprofen, cubic nanoparticles, oral drug delivery, bioavailability
Face-Centered-Cubic Nanostructured Polymer Foams
Cui, C.; Baughman, R. H.; Liu, L. M.; Zakhidov, A. A.; Khayrullin, I. I.
1998-03-01
Beautifully iridescent polymer foams having Fm-3m cubic symmetry and periodicities on the scale of the wavelength of light have been synthesized by the templating of porous synthetic opals. These fabrication processes involve the filling of porous SiO2 opals (with typical cubic lattice parameters of 250 nm) with either polymers or polymer precursors, polymerization of the precursors if necessary, and removal of the fcc array of SiO2 balls to provide an all-polymer structure. The structures of these foams are similar to periodic minimal surfaces, although the Gaussian curvature can have both positive and negative values. Depending upon whether the internal surfaces of the opal are polymer filled or polymer coated, the polymer replica has either one or two sets of independent channels. We fill these channels with semiconductors, metals, or superconductors to provide electronic and optical materials with novel properties dependent on the nanoscale periodicity.
Cubic Polynomials with Rational Roots and Critical Points
Gupta, Shiv K.; Szymanski, Waclaw
2010-01-01
If you want your students to graph a cubic polynomial, it is best to give them one with rational roots and critical points. In this paper, we describe completely all such cubics and explain how to generate them.
Use of Pom Pons to Illustrate Cubic Crystal Structures.
Cady, Susan G.
1997-01-01
Describes a method that uses olefin pom pons to illustrate cubic crystal structure. Facilitates hands-on examination of different packing arrangements such as hexagonal close-packed and cubic close-packed structures. (JRH)
Shape preserving rational bi-cubic function
Directory of Open Access Journals (Sweden)
Malik Zawwar Hussain
2012-11-01
Full Text Available The study is dedicated to the development of shape preserving interpolation scheme for monotone and convex data. A rational bi-cubic function with parameters is used for interpolation. To preserve the shape of monotone and convex data, the simple data dependent constraints are developed on these parameters in each rectangular patch. The developed scheme of this paper is confined, cheap to run and produce smooth surfaces.
Cubic Lienard Equations with Quadratic Damping (Ⅱ)
Institute of Scientific and Technical Information of China (English)
Yu-quan Wang; Zhu-jun Jing
2002-01-01
Applying Hopf bifurcation theory and qualitative theory, we show that the general cubic Lienard equations with quadratic damping have at most three limit cycles. This implies that the guess in which the system has at most two limit cycles is false. We give the sufficient conditions for the system has at most three limit cycles or two limit cycles. We present two examples with three limit cycles or two limit cycles by using numerical simulation.
Local atomic structure in cubic stabilized zirconia
Energy Technology Data Exchange (ETDEWEB)
Villella, P.; Conradson, S. D.; Espinosa-Faller, F. J.; Foltyn, S. R.; Sickafus, K. E.; Valdez, J. A.; Degueldre, C. A.
2001-09-01
X-ray-absorption fine structure measurements have been used to elucidate the local atomic structure of quaternary Zr, Y, Er, Ce/U cubic stabilized zirconia. These compounds display more complicated local environments than those reported for simpler binary systems. While the shortest cation-O distances are similar to those found in the binary cubic stabilized compounds, responding to the different sizes of the cations, we have identified large distortions in the first-shell oxygen distribution involving long, 2.8--3.2 {angstrom} cation-O distances that are similar to those found in the amorphous phase of zirconium. The cation-cation distributions are also found to be quite complicated (non-Gaussian) and element specific. The U-near neighbor distances are expanded relative to the Ce ions for which it substitutes, consistent with the larger size of the actinide, and the U-cation distribution is also more complicated. In terms of the effects of this substitution on the other cation sites, the local environment around Y is altered while the Zr and Er local environments remain unchanged. These results point out the importance of collective and correlated interactions between the different pairs of cations and the host lattice that are mediated by the local strain fields generated by the different cations. The presence of pair-specific couplings has not been commonly included in previous analyses and may have implications for the stabilization mechanisms of cubic zirconia.
The special symplectic structure of binary cubics
Slupinski, Marcus
2009-01-01
Let $k$ be a field of characteristic not 2 or 3. Let $V$ be the $k$-space of binary cubic polynomials. The natural symplectic structure on $k^2$ promotes to a symplectic structure $\\omega$ on $V$ and from the natural symplectic action of $\\textrm{Sl}(2,k)$ one obtains the symplectic module $(V,\\omega)$. We give a complete analysis of this symplectic module from the point of view of the associated moment map, its norm square $Q$ (essentially the classical discriminant) and the symplectic gradient of $Q$. Among the results are a symplectic derivation of the Cardano-Tartaglia formulas for the roots of a cubic, detailed parameters for all $\\textrm{Sl}(2,k)$ and $\\textrm{Gl}(2,k)$-orbits, in particular identifying a group structure on the set of $\\textrm{Sl}(2,k)$-orbits of fixed nonzero discriminant, and a purely symplectic generalization of the classical Eisenstein syzygy for the covariants of a binary cubic. Such fine symplectic analysis is due to the special symplectic nature inherited from the ambient excepti...
Choi, Seung Ho; Kang, Yun Chan
2014-02-26
A continuous one-pot method was employed to synthesize yolk-shell and single-crystalline cubic NiO powders in a few seconds. Submicrometer-sized NiO yolk-shell particles were prepared by spray pyrolysis at 900 °C. Single-crystalline cubic NiO nanopowders were prepared by one-pot flame spray pyrolysis from NiO vapors. Particle surface areas of the yolk-shell and single-crystalline cubic NiO powders as obtained using the Brunauer-Emmett-Teller method were 8 and 5 m(2) g(-1), respectively. The mean crystallite sizes of the yolk-shell-structured and cubic NiO powders were 50 and 80 nm, respectively. The yolk-shell and single-crystalline cubic NiO powders delivered discharge capacities of 951 and 416 mA h g(-1), respectively, after 150 cycles, and the corresponding capacity retentions measured after the first cycle were 106 and 66%, respectively. The yolk-shell-structured NiO powders showed rate performance better than that of the single-crystalline cubic NiO nanopowders. Even at a high current density of 1 A g(-1), the discharge capacity of the yolk-shell-structured NiO powders was as high as 824 mA h g(-1) after 50 cycles, in which the current densities were increased stepwise.
Cherenkov and Scintillation Properties of Cubic Zirconium
Christl, M.J.; Adams, J.H.; Parnell, T.A.; Kuznetsov, E.N.
2008-01-01
Cubic zirconium (CZ) is a high index of refraction (n =2.17) material that we have investigated for Cherenkov counter applications. Laboratory and proton accelerator tests of an 18cc sample of CZ show that the expected fast Cherenkov response is accompanied by a longer scintillation component that can be separated by pulse shaping. This presents the possibility of novel particle spectrometers which exploits both properties of CZ. Other high index materials being examined for Cherenkov applications will be discussed. Results from laboratory tests and an accelerator exposure will be presented and a potential application in solar energetic particle instruments will be discussed
Tachyon Vacuum in Cubic Superstring Field Theory
Erler, Theodore
2008-01-01
In this paper we give an exact analytic solution for tachyon condensation in the modified (picture 0) cubic superstring field theory. We prove the absence of cohomology and, crucially, reproduce the correct value for the D-brane tension. The solution is surprising for two reasons: First, the existence of a tachyon vacuum in this theory has not been definitively established in the level expansion. Second, the solution {\\it vanishes} in the GSO$(-)$ sector, implying a ``tachyon vacuum'' solution exists even for a {\\it BPS} D-brane.
Generalized fairing algorithm of parametric cubic splines
Institute of Scientific and Technical Information of China (English)
WANG Yuan-jun; CAO Yuan
2006-01-01
Kjellander has reported an algorithm for fairing uniform parametric cubic splines. Poliakoff extended Kjellander's algorithm to non-uniform case. However, they merely changed the bad point's position, and neglected the smoothing of tangent at bad point. In this paper, we present a fairing algorithm that both changed point's position and its corresponding tangent vector. The new algorithm possesses the minimum property of energy. We also proved Poliakoff's fairing algorithm is a deduction of our fairing algorithm. Several fairing examples are given in this paper.
Fractal Symmetries: Ungauging the Cubic Code
Williamson, Dominic J
2016-01-01
Gauging is a ubiquitous tool in many-body physics. It allows one to construct highly entangled topological phases of matter from relatively simple phases and to relate certain characteristics of the two. Here we develop a gauging procedure for general submanifold symmetries of Pauli Hamiltonians, including symmetries of fractal type. We show a relation between the pre- and post- gauging models and use this to construct short range entangled phases with fractal like symmetries, one of which is mapped to the cubic code by the gauging.
The Exact Limit of Some Cubic Towers
DEFF Research Database (Denmark)
Anbar Meidl, Nurdagül; Beelen, Peter; Nguyen, Nhut
2016-01-01
Recently, a new explicit tower of function fields was introduced by Bassa, Beelen, Garcia and Stichtenoth (BBGS). This resulted in currently the best known lower bound for Ihara’s constant in the case of non-prime finite fields. In particular over cubic fields, the tower’s limit is at least as good...... as Zink’s bound; i.e. λ(BBGS/Fq3 ) ≥ 2(q2 - 1)/(q + 2). In this paper, the exact value of λ(BBGS/Fq3 ) is computed. We also settle a question stated by Ihara....
Competing structural instabilities in cubic perovskites
Vanderbilt, D
1994-01-01
We study the antiferrodistortive instability and its interaction with ferroelectricity in cubic perovskite compounds. Our first-principles calculations show that coexistence of both instabilities is very common. We develop a first-principles scheme to study the thermodynamics of these compounds when both instabilities are present, and apply it to SrTiO$_3$. We find that increased pressure enhances the antiferrodistortive instability while suppressing the ferroelectric one. Moreover, the presence of one instability tends to suppress the other. A very rich $P$--$T$ phase diagram results.
Rheological properties of Cubic colloidal suspensions
Boromand, Arman; Maia, Joao
2016-11-01
Colloidal and non-colloidal suspensions are ubiquitous in many industrial application. There are numerous studies on these systems to understand and relate their complex rheological properties to their microstructural evolution under deformation. Although most of the experimental and simulation studies are centered on spherical particles, in most of the industrial applications the geometry of the colloidal particles deviate from the simple hard sphere and more complex geometries exist. Recent advances in microfabrication paved the way to fabricate colloidal particles with complex geometries for applications in different areas such as drug delivery where the fundamental understanding of their dynamics has remained unexplored. In this study, using dissipative particle dynamics, we investigate the rheological properties of cubic (superball) particles which are modeled as the cluster of core-modified DPD particles. Explicit representation of solvent particles in the DPD scheme will conserve the full hydrodynamic interactions between colloidal particles. Rheological properties of these cubic suspensions are investigated in the dilute and semi-dilute regimes. The Einstein and Huggins coefficients for these particles with different superball exponent will be calculate which represent the effect of single particle's geometry and multibody interactions on viscosity, respectively. The response of these suspensions is investigated under simple shear and oscillatory shear where it is shown that under oscillation these particles tend to form crystalline structure giving rise to stronger shear-thinning behavior recently measured experimentally.
Zhang, Tingting; Zhao, Kun; Yu, Jiaguo; Jin, Jian; Qi, Yang; Li, Huiquan; Hou, Xinjuan; Liu, Gang
2013-08-01
Potassium niobate (KNbO3) microcubes with orthorhombic and tetragonal phases were hydrothermally prepared and characterized by powder X-ray diffraction, nitrogen adsorption-desorption, micro-Raman spectroscopy, Fourier transform infrared spectroscopy, diffuse reflectance UV-visible spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy. The photoreactivity of the as-prepared KNbO3 samples was evaluated regarding the hydrogen evolution from aqueous methanol under UV, and the results were compared with that of cubic KNbO3 microcubes. The photocatalytic reactivity was shown to be phase-dependent, following the order cubic > orthorhombic > tetragonal. Insight into the phase-dependent photocatalytic properties was gained by first-principles density functional calculations. The best photocatalytic performance of cubic KNbO3 is ascribed to it having the highest symmetry in the bulk structure and associated unique electronic structure. Further, the surface electronic structure plays a key role leading to the discrepancy in photoreactivity between orthorhombic and tetragonal KNbO3. The results from this study are potentially applicable to a range of perovskite-type mixed metal oxides useful in water splitting as well as other areas of heterogeneous photocatalysis.Potassium niobate (KNbO3) microcubes with orthorhombic and tetragonal phases were hydrothermally prepared and characterized by powder X-ray diffraction, nitrogen adsorption-desorption, micro-Raman spectroscopy, Fourier transform infrared spectroscopy, diffuse reflectance UV-visible spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy. The photoreactivity of the as-prepared KNbO3 samples was evaluated regarding the hydrogen evolution from aqueous methanol under UV, and the results were compared with that of cubic KNbO3 microcubes. The photocatalytic reactivity was
All unitary cubic curvature gravities in D dimensions
Energy Technology Data Exchange (ETDEWEB)
Sisman, Tahsin Cagri; Guellue, Ibrahim; Tekin, Bayram, E-mail: sisman@metu.edu.tr, E-mail: e075555@metu.edu.tr, E-mail: btekin@metu.edu.tr [Department of Physics, Middle East Technical University, 06531 Ankara (Turkey)
2011-10-07
We construct all the unitary cubic curvature gravity theories built on the contractions of the Riemann tensor in D-dimensional (anti)-de Sitter spacetimes. Our construction is based on finding the equivalent quadratic action for the general cubic curvature theory and imposing ghost and tachyon freedom, which greatly simplifies the highly complicated problem of finding the propagator of cubic curvature theories in constant curvature backgrounds. To carry out the procedure we have also classified all the unitary quadratic models. We use our general results to study the recently found cubic curvature theories using different techniques and the string generated cubic curvature gravity model. We also study the scattering in critical gravity and give its cubic curvature extensions.
Yang, Tao; Zhang, Liqin; Hou, Xinmei; Chen, Junhong; Chou, Kuo-Chih
2016-04-25
Fabrication of eletrochemical sensors based on wide bandgap compound semiconductors has attracted increasing interest in recent years. Here we report for the first time electrochemical nitrite sensors based on cubic silicon carbide (SiC) nanowires (NWs) with smooth surface and boron-doped cubic SiC NWs with fin-like structure. Multiple techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electron energy loss spectroscopy (EELS) were used to characterize SiC and boron-doped SiC NWs. As for the electrochemical behavior of both SiC NWs electrode, the cyclic voltammetric results show that both SiC electrodes exhibit wide potential window and excellent electrocatalytic activity toward nitrite oxidation. Differential pulse voltammetry (DPV) determination reveals that there exists a good linear relationship between the oxidation peak current and the concentration in the range of 50-15000 μmoL L(-1) (cubic SiC NWs) and 5-8000 μmoL L(-1) (B-doped cubic SiC NWs) with the detection limitation of 5 and 0.5 μmoL L(-1) respectively. Compared with previously reported results, both as-prepared nitrite sensors exhibit wider linear response range with comparable high sensitivity, high stability and reproducibility.
Cubic meter volume optical coherence tomography
WANG, ZHAO; POTSAID, BENJAMIN; CHEN, LONG; DOERR, CHRIS; LEE, HSIANG-CHIEH; NIELSON, TORBEN; JAYARAMAN, VIJAYSEKHAR; CABLE, ALEX E.; SWANSON, ERIC; FUJIMOTO, JAMES G.
2017-01-01
Optical coherence tomography (OCT) is a powerful three-dimensional (3D) imaging modality with micrometer-scale axial resolution and up to multi-GigaVoxel/s imaging speed. However, the imaging range of high-speed OCT has been limited. Here, we report 3D OCT over cubic meter volumes using a long coherence length, 1310 nm vertical-cavity surface-emitting laser and silicon photonic integrated circuit dual-quadrature receiver technology combined with enhanced signal processing. We achieved 15 µm depth resolution for tomographic imaging at a 100 kHz axial scan rate over a 1.5 m range. We show 3D macroscopic imaging examples of a human mannequin, bicycle, machine shop gauge blocks, and a human skull/brain model. High-bandwidth, meter-range OCT demonstrates new capabilities that promise to enable a wide range of biomedical, scientific, industrial, and research applications. PMID:28239628
Black holes in Einsteinian cubic gravity
Hennigar, Robie A
2016-01-01
Using numerical and perturbative methods, we construct the first examples of black hole solutions in Einsteinian cubic gravity and study their thermodynamics. Focusing first on four dimensional solutions, we show that these black holes have a novel equation of state in which the pressure is a quadratic function of the temperature. Despite this, they undergo a first order phase transition with associated van der Waals behaviour. We then construct perturbative solutions for general $D \\ge 5$ and study the properties of these solutions for $D=5$ and $D=6$ in particular. We find novel examples of zeroth order phase transitions and find super-entropic behaviour over a large portion of the parameter space. We analyse the specific heat, determining that the black holes are thermodynamically stable over large regions of parameter space.
Triangulation of cubic panorama for view synthesis.
Zhang, Chunxiao; Zhao, Yan; Wu, Falin
2011-08-01
An unstructured triangulation approach, new to our knowledge, is proposed to apply triangular meshes for representing and rendering a scene on a cubic panorama (CP). It sophisticatedly converts a complicated three-dimensional triangulation into a simple three-step triangulation. First, a two-dimensional Delaunay triangulation is individually carried out on each face. Second, an improved polygonal triangulation is implemented in the intermediate regions of each of two faces. Third, a cobweblike triangulation is designed for the remaining intermediate regions after unfolding four faces to the top/bottom face. Since the last two steps well solve the boundary problem arising from cube edges, the triangulation with irregular-distribution feature points is implemented in a CP as a whole. The triangular meshes can be warped from multiple reference CPs onto an arbitrary viewpoint by face-to-face homography transformations. The experiments indicate that the proposed triangulation approach provides a good modeling for the scene with photorealistic rendered CPs.
Black holes in a cubic Galileon universe
Babichev, Eugeny; Lehébel, Antoine; Moskalets, Tetiana
2016-01-01
We find and study the properties of black hole solutions for a subclass of Horndeski theory including the cubic Galileon term. The theory under study has shift symmetry but not reflection symmetry for the scalar field. The Galileon is assumed to have linear time dependence characterized by a velocity parameter. We give analytic 3-dimensional solutions that are akin to the BTZ solutions but with a non-trivial scalar field that modifies the effective cosmological constant. We then study the 4-dimensional asymptotically flat and de Sitter solutions. The latter present three different branches according to their effective cosmological constant. For two of these branches, we find families of black hole solutions, parametrized by the velocity of the scalar field. These spherically symmetric solutions, obtained numerically, are different from GR solutions close to the black hole event horizon, while they have the same de-Sitter asymptotic behavior. The velocity parameter represents black hole primary hair.
Finite element differential forms on cubical meshes
Arnold, Douglas N
2012-01-01
We develop a family of finite element spaces of differential forms defined on cubical meshes in any number of dimensions. The family contains elements of all polynomial degrees and all form degrees. In two dimensions, these include the serendipity finite elements and the rectangular BDM elements. In three dimensions they include a recent generalization of the serendipity spaces, and new H(curl) and H(div) finite element spaces. Spaces in the family can be combined to give finite element subcomplexes of the de Rham complex which satisfy the basic hypotheses of the finite element exterior calculus, and hence can be used for stable discretization of a variety of problems. The construction and properties of the spaces are established in a uniform manner using finite element exterior calculus.
Capturing dynamic cation hopping in cubic pyrochlores
Brooks Hinojosa, Beverly; Asthagiri, Aravind; Nino, Juan C.
2011-08-01
In direct contrast to recent reports, density functional theory predicts that the most stable structure of Bi2Ti2O7 pyrochlore is a cubic Fd3¯m space group by accounting for atomic displacements. The displaced Bi occupies the 96g(x,x,z) Wyckoff position with six equivalent sites, which create multiple local minima. Using nudged elastic band method, the transition states of Bi cation hopping between equivalent minima were investigated and an energy barrier between 0.11 and 0.21 eV was determined. Energy barriers associated with the motion of Bi between equivalent sites within the 96g Wyckoff position suggest the presence of dielectric relaxation in Bi2Ti2O7.
On the plane-wave cubic vertex
Lucietti, J; Sinha, A K; Lucietti, James; Schäfer-Nameki, Sakura; Sinha, Aninda
2004-01-01
The exact bosonic Neumann matrices of the cubic vertex in plane-wave light-cone string field theory are derived using the contour integration techniques developed in our earlier paper. This simplifies the original derivation of the vertex. In particular, the Neumann matrices are written in terms of \\mu-deformed Gamma-functions, thus casting them into a form that elegantly generalizes the well-known flat-space solution. The asymptotics of the \\mu-deformed Gamma-functions allow one to determine the large-\\mu behaviour of the Neumann matrices including exponential corrections. We provide an explicit expression for the first exponential correction and make a conjecture for the subsequent exponential correction terms.
Polarization conversion in cubic Raman crystals
McKay, Aaron; Sabella, Alexander; Mildren, Richard P.
2017-01-01
Nonlinear conversion of unpolarized beams to lower frequencies is generally inefficient in c(2) materials, as it is challenging to achieve phase-matching for input ordinary and extraordinary beams simultaneously in the normal dispersion regime. Here, we show that cubic Raman crystals having doubly and triply degenerate (E and F type) modes provide a method for efficient nonlinear frequency downconversion of an unpolarized beam and yield a linearly polarized output state. Using Mueller calculus, optimal crystal directions for such polarization conversion are determined. Using diamond, an example of an F-class Raman crystal, we have verified that such conversion is possible with near quantum-defect-limited slope efficiency and a linear polarization contrast of more than 23.9 dB. PMID:28169327
On the Stability of Cubic Galileon Accretion
Bergliaffa, Santiago P E
2016-01-01
We examine the stability of steady-state galileon accretion for the case of a Schwarzshild black hole. Considering the galileon action up to the cubic term in a static and spherically symmetric background we obtain the general solution for the equation of motion which is divided in two branches. By perturbing this solution we define an effective metric which determines the propagation of fluctuations. In this general picture we establish the position of the sonic horizon together with the matching condition of the two branches on it. Restricting to the case of a Schwarzschild background, we show, via the analysis of the energy of the perturbations and its time derivative, that the accreting field is linearly stable.
Low pressure growth of cubic boron nitride films
Ong, Tiong P. (Inventor); Shing, Yuh-Han (Inventor)
1997-01-01
A method for forming thin films of cubic boron nitride on substrates at low pressures and temperatures. A substrate is first coated with polycrystalline diamond to provide a uniform surface upon which cubic boron nitride can be deposited by chemical vapor deposition. The cubic boron nitride film is useful as a substitute for diamond coatings for a variety of applications in which diamond is not suitable. any tetragonal or hexagonal boron nitride. The cubic boron nitride produced in accordance with the preceding example is particularly well-suited for use as a coating for ultra hard tool bits and abrasives, especially those intended to use in cutting or otherwise fabricating iron.
Shape preserving rational cubic spline for positive and convex data
Directory of Open Access Journals (Sweden)
Malik Zawwar Hussain
2011-11-01
Full Text Available In this paper, the problem of shape preserving C2 rational cubic spline has been proposed. The shapes of the positive and convex data are under discussion of the proposed spline solutions. A C2 rational cubic function with two families of free parameters has been introduced to attain the C2 positive curves from positive data and C2 convex curves from convex data. Simple data dependent constraints are derived on free parameters in the description of rational cubic function to obtain the desired shape of the data. The rational cubic schemes have unique representations.
Kang, Gyeong Pil; Lee, Kyounghoon; Kim, Yong Hwan; Park, Sang Jun; Shin, Kwang Seon
2017-09-01
A methodology on the multiscale simulation of metal forming processes is presented, which fully integrates the visco-plastic self-consistent (VPSC) polycrystal model into rigid plastic finite element method (FEM). To accurately predict the material behavior of a magnesium alloy from the microstructural level, the VPSC crystal plasticity model was used as a constitutive equation in this methodology. An optimization program VPSC-GA was developed in order to calculate the hardening parameters for each slip and twin mode of a single crystal from a couple of simple tension/compression tests. The existing constitutive equation for rigid plastic FEM is modified using the deviatoric stress components and the derivatives of them with respect to strain rate components. The stiffness matrix and the load vector were derived based on a new approach and implemented into DEFORMTM-3D via a user subroutine which handles stiffness matrix in elemental level. An application to the Erichsen tests of magnesium alloys was done and the stretch formability of two different Mg alloy sheets was analyzed using the results of both experiment and simulation.
Matsumoto, Naoya; Yoshinari, Masao; Takemoto, Shinji; Hattori, Masayuki; Kawada, Eiji; Oda, Yutaka
2013-01-01
The purpose of the present study was to investigate the influence of the intermediate ceramics and firing temperature on bond strength between tetragonal zirconia polycrystal (TZP) and its intermediate ceramics. Two types of intermediate ceramics, defined as a ceramics placed between the TZP and its veneering ceramics, were used; one including high-strength lithium-disilicate (EP) or feldspathic liner porcelain (SB). The firing temperature of the intermediate ceramics was set at 930°C, 945°C or 960°C. Shear bond strength showed values of 35.8 MPa in SB and 54.9 MPa in EP at a firing temperature of 960°C. Electron probe microanalysis revealed that components of the intermediate ceramics remained on the TZP surface after debonding, indicating that fractures occurred in the intermediate ceramics near the TZP. These results indicate that the bond strength between and a TZP framework and its veneering ceramics could be improved by using a high-strength intermediate ceramics and a comparatively high firing temperature.
Energy Technology Data Exchange (ETDEWEB)
Palancher, H., E-mail: herve.palancher@cea.fr [CEA, DEN, DEC, F-13108 St. Paul Lez Durance Cedex (France); Kachnaoui, R.; Martin, G. [CEA, DEN, DEC, F-13108 St. Paul Lez Durance Cedex (France); Richard, A. [CEA, DEN, DEC, F-13108 St. Paul Lez Durance Cedex (France); Institut Pprime, CNRS-Universite de Poitiers–ENSMA, SP2MI, F-86360 Chasseneuil (France); Richaud, J.-C.; Onofri, C.; Belin, R. [CEA, DEN, DEC, F-13108 St. Paul Lez Durance Cedex (France); Boulle, A. [Science des Procedes Ceramiques et Traitements de Surface (SPCTS), CNRS UMR 7315, Centre Europeen de la Ceramique, 12 rue Atlantis, 87068 Limoges (France); Rouquette, H.; Sabathier, C.; Carlot, G. [CEA, DEN, DEC, F-13108 St. Paul Lez Durance Cedex (France); Desgardin, P.; Sauvage, T. [CNRS-CEMHTI, UPR3079, 45071 Orléans (France); Rieutord, F. [CEA, DSM, INAC, F-38054 Grenoble Cedex 9 (France); Raynal, J. [CEA, DEN, DEC, F-13108 St. Paul Lez Durance Cedex (France); Goudeau, Ph. [Institut Pprime, CNRS-Universite de Poitiers–ENSMA, SP2MI, F-86360 Chasseneuil (France); Ambard, A. [EDF, R& D Division, Les Renardières, 77818 Morez-sur-Loing (France)
2016-08-01
Within the frame of the long-term evolution of spent nuclear fuel in dry disposal, the behavior of He in UO{sub 2} polycrystals has to be studied. Here, strain relaxation in He implanted samples has been characterized using in situ X-ray diffraction during thermal annealing. The influence of a wide range of experimental parameters (annealing atmosphere, He ion energy, orientation of the UO{sub 2} grains probed by X-rays) has been evaluated. If each of them contributes to the strain relaxation kinetics in the implanted layer, strain relaxation is not completed for temperatures below 900 °C which is equivalent to what has been found on He implanted UO{sub 2} single crystals, or aged UO{sub 2} pellets doped with α-emitters. In the case of implantation with 500 keV He ions, we clearly show that strain relaxation and He release are not correlated for temperatures below 750 °C.
Risse, Marcel; Lentz, Martin; Fahrenson, Christoph; Reimers, Walter; Knezevic, Marko; Beyerlein, Irene J.
2017-01-01
In this work, we study the deformation behavior of Mg-4 wt pct Li in uniaxial tension as a function of temperature and loading direction. Standard tensile tests were performed at temperatures in the range of 293 K (20 °C) ≤ T ≤ 473 K (200 °C) and in two in-plane directions: the extrusion and the transverse. We find that while the in-plane plastic anisotropy (PA) decreases with temperature, the anisotropy in failure strain and texture development increases. To uncover the temperature dependence in the critical stresses for slip and in the amounts of slip and twinning systems mediating deformation, we employ the elastic-plastic self-consistent polycrystal plasticity model with a thermally activated dislocation density based hardening law for activating slip with individual crystals. We demonstrate that the model, with a single set of intrinsic material parameters, achieves good agreement with the stress-strain curves, deformation textures, and intragranular misorientation axis analysis for all test directions and temperatures. With the model, we show that at all temperatures the in-plane tensile behavior is driven primarily by analysis explains that the in-plane PA decreases and failure strains increase with temperature as a result of a significant reduction in the activation stress for pyramidal effectively promotes strain accommodation from multiple types of mode, and basal slip in the other. These findings reveal the relationship between the temperature-sensitive thresholds needed to activate crystallographic slip and the development of texture and macroscopic PA.
Pinto, Palena A; Colas, Guillaume; Filleter, Tobin; De Souza, Grace M
2016-12-01
Yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP) is a ceramic material used in indirect dental restorations. However, phase transformation at body temperature may compromise the material's mechanical properties, affecting the clinical performance of the restoration. The effect of mastication on 3Y-TZP aging has not been investigated. 3Y-TZP specimens (IPS E-max ZirCAD and Z5) were aged in three different modes (n=13): no aging (control), hydrothermal aging (HA), or chewing simulation (CS). Mechanical properties and surface topography were analyzed. Analysis of variance showed that neither aging protocol (p=0.692) nor material (p=0.283) or the interaction between them (p=0.216) had a significant effect on flexural strength, values ranged from 928.8 MPa (IPSHA) to 1,080.6 MPa (Z5HA). Nanoindentation analysis showed that material, aging protocol, and the interaction between them had a significant effect (p<0.001) on surface hardness and reduced Young's modulus. The compositional analysis revealed similar yttrium content for all the experimental conditions (aging: p=0.997; material: p=0.248; interaction material×aging: p=0.720). Atomic force microscopy showed an effect of aging protocols on phase transformation, with samples submitted to CS exhibiting features compatible with maximized phase transformation, such as increased volume of the material microstructure at the surface leading to an increase in surface roughness.
Alao, Abdur-Rasheed; Stoll, Richard; Song, Xiao-Fei; Miyazaki, Takashi; Hotta, Yasuhiro; Shibata, Yo; Yin, Ling
2017-01-01
This paper studied the surface quality (damage, morphology, and phase transformation) of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) in CAD/CAM milling, and subsequent polishing, sintering and sandblasting processes applied in dental restorations. X-ray diffraction and scanning electron microscopy (SEM) were used to scan all processed surfaces to determine phase transformations and analyse surface damage morphology, respectively. The average surface roughness (Ra) and maximum roughness (Rz) for all processed surfaces were measured using desk-top SEM-assisted morphology analytical software. X-ray diffraction patterns prove the sintering-induced monoclinic-tetragonal phase transformation while the sandblasting-induced phase transformation was not detected. The CAD/CAM milling of pre-sintered Y-TZP produced very rough surfaces with extensive fractures and cracks. Simply polishing or sintering of milled pre-sintered surfaces did not significantly improve their surface roughness (ANOVA, p>0.05). Neither sintering-polishing of the milled surfaces could effectively improve the surface roughness (ANOVA, p>0.05). The best surface morphology was produced in the milling-polishing-sintering process, achieving Ra=0.21±0.03µm and Rz=1.73±0.04µm, which meets the threshold for bacterial retention. Sandblasting of intaglios with smaller abrasives was recommended as larger abrasive produced visible surface defects. This study provides technical insights into process selection for Y-TZP to achieve the improved restorative quality.
Geometrical Effect in Magneto-Peltier Cooling of Bi and Bi0.88Sb0.12 Polycrystals
Yamashita, Osamu; Tomiyoshi, Shoichi
2002-10-01
The cooling temperatures of rectangular parallelepiped Bi and Bi0.88Sb0.12 polycrystals with various widths W and thickness t were measured at 293 K as a function of electric current in the magnetic field B up to 2.17 T, where the magnetic field is aligned along the thickness of a sample and the current flows along its length L through the copper leads soldered to both end whole surfaces of the cross section (W× t). Under such a configuration the temperatures were measured at both end surfaces. A thermoelement is not in contact with a heat sink. The cooling temperature at the cooled surface increased with increasing the magnetic field, and the rate of increase depended strongly on the cross-sectional area (W× t) of a sample, particularly in high magnetic fields. The highest cooling temperature was found to be achieved when a thermoelement has an optimum cross-sectional area (fitted to its length) so that Joule heating and the thermal conduction energies become equal under the operating conditions. The cooling temperature of Bi0.88Sb0.12 with optimum dimensions increased from 3.1 K in B=0 T to 6.4 K in B=± 2.17 T, so that it slightly exceeded a cooling temperature of 5.7 K which was obtained for a typical Bi2Te3 with a thermoelectric figure of merit of ZT=0.87 at 298 K.
N2 plasma etching processes of microscopic single crystals of cubic boron nitride
Tamura, Takahiro; Takami, Takuya; Yanase, Takashi; Nagahama, Taro; Shimada, Toshihiro
2017-06-01
We studied the N2 plasma etching of cubic boron nitride (cBN). We have developed experimental techniques for handling 200-µm-size single crystals for the preparation of surfaces with arbitrary crystal indexes, plasma processes, and surface analyses. We successfully prepared smooth surfaces of cBN with roughness smaller than 10 nm and found that the etching behavior was strongly influenced by the surface indexes. The morphology of the etched surfaces can be explained by the chemical stability of (111)B surfaces.
CRACK PROBLEM UNDER SHEAR LOADING IN CUBIC QUASICRYSTAL
Institute of Scientific and Technical Information of China (English)
周旺民; 范天佑; 尹姝媛
2003-01-01
The axisymmetric elasticity problem of cubic quasicrystal is reduced to a single higher-order partial differential equation by introducing a displacement function. Based on the work, the analytic solutions of elastic field of cubic quasicrystal with a penny-shaped crack under the shear loading are found, and the stress intensity factor and strain energy release rate are determined.
Cubic Polynomials with Real or Complex Coefficients: The Full Picture
Bardell, Nicholas S.
2016-01-01
The cubic polynomial with real coefficients has a rich and interesting history primarily associated with the endeavours of great mathematicians like del Ferro, Tartaglia, Cardano or Vieta who sought a solution for the roots (Katz, 1998; see Chapter 12.3: The Solution of the Cubic Equation). Suffice it to say that since the times of renaissance…
An application of Cubical Cohomology to Adinkras and Supersymmetry Representations
Doran, Charles; Landweber, Greg
2012-01-01
An Adinkra is a class of graphs with certain signs marking its vertices and edges, which encodes off-shell representations of the super Poincar\\'e algebra. The markings on the vertices and edges of an Adinkra are cochains for cubical cohomology. This article explores the cubical cohomology of Adinkras, treating these markings analogously to characteristic classes on smooth manifolds.
Diamine Functionalized Cubic Mesoporous Silica for Ibuprofen Controlled Delivery.
Sivaguru, J; Selvaraj, M; Ravi, S; Park, H; Song, C W; Chun, H H; Ha, C-S
2015-07-01
A diamine functionalized cubic mesostructured KIT-6 (N-KIT-6) has been prepared by post-synthetic method using calcined mesoporous KIT-6 with a diamine source, i.e., N-'[3-(tri methoxysilyl)- propyl]'ethylenediamine. The KIT-6 mesoporous silica used for N-KIT-6 was synthesized under weak acidic hydrothermal method using bitemplates, viz., Pluronic P123 and 1-butanol. The synthesized mesoporous materials, KIT-6 and N-KIT-6, have been characterized by the relevant instrumental techniques such as SAXS, N2 sorption isotherm, FT-IR, SEM, TEM and TGA to prove the standard mesoporous materials with the identification of diamine groups. The characterized mesoporous materials, KIT-6 and N-KIT-6, have been extensively used in the potential application of controlled drug delivery, where ibuprofen (IBU) employed as a model drug. The rate of IBU adsorption and release was monitored by UV vis-spectrometer. On the basis of the experimental results of controlled drug delivery system, the results of IBU adsorption and releasing rate in N-KIT-6 are higher than those of KIT-6 because of the higher hydrophobic nature as well as rich basic sites on the surface of inner pore wall silica.
Rational Cubics and Conics Representation: A Practical Approach
Directory of Open Access Journals (Sweden)
M. Sarfraz
2012-08-01
Full Text Available A rational cubic spline, with one family of shape parameters, has been discussed with the view to its application in Computer Graphics. It incorporates both conic sections and parametric cubic curves as special cases. The parameters (weights, in the description of the spline curve can be used to modify the shape of the curve, locally and globally, at the knot intervals. The rational cubic spline attains parametric smoothness whereas the stitching of the conic segments preserves visually reasonable smoothness at the neighboring knots. The curve scheme is interpolatory and can plot parabolic, hyperbolic, elliptic, and circular splines independently as well as bits and pieces of a rational cubic spline.Key Words: Computer Graphics, Interpolation, Spline, Conic, Rational Cubic
On cubic equations over $P-$adic field
Mukhamedov, Farrukh; Saburov, Mansoor
2012-01-01
We provide a solvability criteria for a depressed cubic equation in domains $\\bz_p^{*},\\bz_p,\\bq_p$. We show that, in principal, the Cardano method is not always applicable for such equations. Moreover, the numbers of solutions of the depressed cubic equation in domains $\\bz_p^{*},\\bz_p,\\bq_p$ are provided. Since $\\bbf_p\\subset\\bq_p,$ we generalize J.-P. Serre's \\cite{JPSJ} and Z.H.Sun's \\cite{ZHS1,ZHS3} results concerning with depressed cubic equations over the finite field $\\bbf_p$. Finally, all depressed cubic equations, for which the Cardano method could be applied, are described and the $p-$adic Cardano formula is provided for those cubic equations.
Energy Technology Data Exchange (ETDEWEB)
Seetha, M., E-mail: seetha.phy@gmail.com [Department of Physics, SRM University, Kattankulathur, Kancheepuram Dt 603 203 (India); Meena, P. [Department of Physics, PSGR Krishnammal College for Women, Coimbatore 641 046 (India); Mangalaraj, D., E-mail: dmraj800@yahoo.com [DRDO-BU Centre for Life Sciences, Bharathiar University Campus, Coimbatore (India); Department of Nanoscience and Technology, Bharathiar University, Coimbatore 641 014 (India); Masuda, Yoshitake [National Institute of Advanced Industrial Science and Technology (AIST), Nagoya 463-8560 (Japan); Senthil, K. [School of Advanced Materials Science and Engineering, Sungkyunkwan University (Suwon Campus), Cheoncheon-dong 300, Jangan-gu, Suwon 440-746 (Korea, Republic of)
2012-03-15
Highlights: Black-Right-Pointing-Pointer For the first time HMT is used in the preparation of indium oxide. Black-Right-Pointing-Pointer HMT itself acts as base for the precursor and results in cubic indium hydroxide. Black-Right-Pointing-Pointer Modified hydrothermal route used for the preparation of cubic indium oxide crystals. Black-Right-Pointing-Pointer As a new approach a composite film synthesized with prepared indium oxide. Black-Right-Pointing-Pointer Film showed good response to ethanol vapours with quick response and recovery times. - Abstract: Indium oxide cubic crystals were prepared by using hexamethylenetetramine and indium chloride without the addition of any structure directing agents. The chemical route followed in the present work was a modified hydrothermal synthesis. The average crystallite size of the prepared cubes was found to be 40 nm. A blue emission at 418 nm was observed at room temperature when the sample was excited with a 380 nm Xenon lamp. This emission due to oxygen vacancies made the material suitable for gas sensing applications. The synthesized material was made as a composite film with polyvinyl alcohol which was more flexible than the films prepared on glass substrates. This flexible film was used as a sensing element and tested with ethanol vapours at room temperature. The film showed fast response as well as recovery to ethanol vapours with a sensor response of about 1.4 for 100 ppm of the gas.
Theory and calculus of cubical complexes
Perlman, M.
1973-01-01
Combination switching networks with multiple outputs may be represented by Boolean functions. Report has been prepared which describes derivation and use of extraction algorithm that may be adapted to simplification of such simultaneous Boolean functions.
Magnetic properties of cubic FeCo nanoparticles with anisotropic long chain structure
Liu, Jinming; Wu, Kai; Wang, Jian-Ping
2016-05-01
Cubic FeCo alloy nanoparticles (NPs) with body-centered cubic (bcc) phase were prepared using sputter based gas-condensation method. When the NPs formed long chain assemblies, the magnetic properties were quite different from that of well-dispersed NPs. Most of the well-dispersed NPs were superparamagnetic at room temperature while the long chain NP assemblies were ferromagnetic with coercivities around 765 Oe, which displayed quite different magnetic properties. The ferromagnetism of long chain NPs was from the exchange coupling between NPs, which eventually led to the transition from superparamagnetism (SPM) to superferromagetism (SFM). Zero-field-cooled (ZFC) and field-cooled (FC) curves were obtained and long chain NP assemblies displayed ferromagnetism at the temperature ranging from 10 K to 400 K. Time-dependent remanent magnetic moment curves also indicated that the long chain structure had better thermal stability due to the strong exchange coupling.
Magnetic properties of cubic FeCo nanoparticles with anisotropic long chain structure
Directory of Open Access Journals (Sweden)
Jinming Liu
2016-05-01
Full Text Available Cubic FeCo alloy nanoparticles (NPs with body-centered cubic (bcc phase were prepared using sputter based gas-condensation method. When the NPs formed long chain assemblies, the magnetic properties were quite different from that of well-dispersed NPs. Most of the well-dispersed NPs were superparamagnetic at room temperature while the long chain NP assemblies were ferromagnetic with coercivities around 765 Oe, which displayed quite different magnetic properties. The ferromagnetism of long chain NPs was from the exchange coupling between NPs, which eventually led to the transition from superparamagnetism (SPM to superferromagetism (SFM. Zero-field-cooled (ZFC and field-cooled (FC curves were obtained and long chain NP assemblies displayed ferromagnetism at the temperature ranging from 10 K to 400 K. Time-dependent remanent magnetic moment curves also indicated that the long chain structure had better thermal stability due to the strong exchange coupling.
The Body Center Cubic Quark Lattice Model
Lin Xu, Jiao
2004-01-01
The Standard Model while successful in many ways is incomplete; many questions remain. The origin of quark masses and hadronization of quarks are awaiting an answer. From the Dirac sea concept, we infer that two kinds of elementary quarks (u(0) and d(0)) constitute a body center cubic (BCC) quark lattice with a lattice constant a < $10^{-18}$m in the vacuum. Using energy band theory and the BCC quark lattice, we can deduce the rest masses and the intrinsic quantum numbers (I, S, C, b and Q) of quarks. With the quark spectrum, we deduce a baryon spectrum. The theoretical spectrum is in agreement well with the experimental results. Not only will this paper provide a physical basis for the Quark Model, but also it will open a door to study the more fundamental nature at distance scales <$10^{-18}$m. This paper predicts some new quarks $u_{c}$(6490) and d$_{b}$(9950), and new baryons $\\Lambda_{c}^{+}$(6500), $\\Lambda_{b}^{0}$(9960).
Influence of Al on the magnetostriction of Fe-Ga polycrystal alloys under compressive stress
Institute of Scientific and Technical Information of China (English)
Long-long Liao; Mei-ling Fang; Jie Zhu; Ji-heng Li; Jian Wang
2014-01-01
Fe80Ga20-xAlx (x=0, 6, 9, 14) ingots were prepared from high purity elements using a vacuum induction system. X-ray diffraction patterns show that the alloys are A2 disordered structures. The influence of the partial substitution of Ga in Fe-Ga alloys with Al on their magnetostrictive properties was investigated, and the effects of different heat treatment conditions on the magnetostriction and microstructure of the alloy rods were also examined. The saturation magnetostriction value of Fe80Ga20 can reach to 240 × 10-6 under a compressive stress of 20 MPa. The Fe80Ga11Al9 alloy has many good properties, such as low hysteresis, high linearity of the magnetostriction curve, and low saturated magnetic field, which make it a potential candidate for magnetostrictive actuator and transducer applications. It is found that sub-grains have little influence on the magnetostriction of Fe-Ga alloys.
Characterization, Microstructure, and Dielectric properties of cubic pyrochlore structural ceramics
Li, Yangyang
2013-05-01
The (BMN) bulk materials were sintered at 1050°C, 1100°C, 1150°C, 1200°C by the conventional ceramic process, and their microstructure and dielectric properties were investigated by Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, Transmission electron microscopy (TEM) (including the X-ray energy dispersive spectrometry EDS and high resolution transmission electron microscopy HRTEM) and dielectric impedance analyzer. We systematically investigated the structure, dielectric properties and voltage tunable property of the ceramics prepared at different sintering temperatures. The XRD patterns demonstrated that the synthesized BMN solid solutions had cubic phase pyrochlore-type structure when sintered at 1050°C or higher, and the lattice parameter (a) of the unit cell in BMN solid solution was calculated to be about 10.56Å. The vibrational peaks observed in the Raman spectra of BMN solid solutions also confirmed the cubic phase pyrochlore-type structure of the synthesized BMN. According to the Scanning Electron Microscope (SEM) images, the grain size increased with increasing sintering temperature. Additionally, it was shown that the densities of the BMN ceramic tablets vary with sintering temperature. The calculated theoretical density for the BMN ceramic tablets sintered at different temperatures is about 6.7521 . The density of the respective measured tablets is usually amounting more than 91% and 5 approaching a maximum value of 96.5% for sintering temperature of 1150°C. The microstructure was investigated by using Scanning Transmission Electron Microscope (STEM), X-ray diffraction (XRD). Combined with the results obtained from the STEM and XRD, the impact of sintering temperature on the macroscopic and microscopic structure was discussed. The relative dielectric constant ( ) and dielectric loss ( ) of the BMN solid solutions were measured to be 161-200 and (at room temperature and 100Hz-1MHz), respectively. The BMN solid
Agarwal, Sumit; Briant, Clyde L.; Krajewski, Paul E.; Bower, Allan F.; Taleff, Eric M.
2007-04-01
A finite element method was recently designed to model the mechanisms that cause superplastic deformation (A.F. Bower and E. Wininger, A Two-Dimensional Finite Element Method for Simulating the Constitutive Response and Microstructure of Polycrystals during High-Temperature Plastic Deformation, J. Mech. Phys. Solids, 2004, 52, p 1289-1317). The computations idealize the solid as a collection of two-dimensional grains, separated by sharp grain boundaries. The grains may deform plastically by thermally activated dislocation motion, which is modeled using a conventional crystal plasticity law. The solid may also deform by sliding on the grain boundaries, or by stress-driven diffusion of atoms along grain boundaries. The governing equations are solved using a finite element method, which includes a front-tracking procedure to monitor the evolution of the grain boundaries and surfaces in the solid. The goal of this article is to validate these computations by systematically comparing numerical predictions to experimental measurements of the elevated-temperature response of aluminum alloy AA5083 (M.-A. Kulas, W.P. Green, E.M. Taleff, P.E. Krajewski, and T.R. McNelley, Deformation Mechanisms in Superplastic AA5083 materials. Metall. Mater. Trans. A, 2005, 36(5), p 1249-1261). The experimental work revealed that a transition occurs from grain-boundary sliding to dislocation (solute-drag) creep at approximately 0.001/s for temperatures between 425 and 500 °C. In addition, increasing the grain size from 7 to 10 μm decreased the transition to significantly lower strain rates. Predictions from the finite element method accurately predict the effect of grain size on the transition in deformation mechanisms.
Directory of Open Access Journals (Sweden)
Jie Lai
2009-12-01
Full Text Available Jie Lai1,2, Yi Lu1, Zongning Yin2, Fuqiang Hu3, Wei Wu11School of Pharmacy, Fudan University, Shanghai, China, 2West China School of Pharmacy, Sichuan University, Chengdu, China, 3School of Pharmacy, Zhejiang University, Hangzhou, ChinaAbstract: Efforts to improve the oral bioavailability of cyclosporine A (CyA remains a challenge in the field of drug delivery. In this study, glyceryl monooleate (GMO/poloxamer 407 cubic nanoparticles were evaluated as potential vehicles to improve the oral bioavailability of CyA. Cubic nanoparticles were prepared via the fragmentation of a bulk GMO/poloxamer 407 cubic phase gel by sonication and homogenization. The cubic inner structure formed was verified using Cryo-TEM. The mean diameters of the nanoparticles were about 180 nm, and the entrapment efficiency of these particles for CyA was over 85%. The in vitro release of CyA from these nanoparticles was less than 5% at 12 h. The results of a pharmacokinetic study in beagle dogs showed improved absorption of CyA from cubic nanoparticles as compared to microemulsion-based Neoral®; higher Cmax (1371.18 ± 37.34 vs 969.68 ± 176.3 ng mL-1, higher AUC0–t (7757.21 ± 1093.64 vs 4739.52 ± 806.30 ng h mL-1 and AUC0–∞ (9004.77 ± 1090.38 vs 5462.31 ± 930.76 ng h mL-1. The relative oral bioavailability of CyA cubic nanoparticles calculated on the basis of AUC0–∞ was about 178% as compared to Neoral®. The enhanced bioavailability of CyA is likely due to facilitated absorption by cubic nanoparticles rather than improved release.Keywords: nanoparticles, cubosomes, cyclosporine A, glyceryl monooleate, oral drug delivery, bioavailability, beagle dogs
The growth of a single crystal of Sr3CuIrO6 and its magnetic behavior compared to polycrystals
Indian Academy of Sciences (India)
Asad Niazi; P L Paulose; E V Sampathkumaran; Ute Ch Rodewald; W Jeitschko
2002-05-01
We have grown single crystals of the psuedo-one-dimensional compound Sr3CuIrO6, a K4CdCl6-derived monoclinic structure with Cu–Ir chains along the [101] direction. We present the ac and dc magnetization behavior of the single crystals in comparison with that of the polycrystalline form reported earlier. There is a distinct evidence for at least two magnetic transitions, at 5 K (1) and 19 K (2), with different relative magnitudes in the single and polycrystals. The low temperature magnetic relaxation behavior of both the forms is found to be widely different, exhibiting unexpected time dependence.
Energy Technology Data Exchange (ETDEWEB)
Maawad, E., E-mail: grossflotbek2000@gmail.com [Helmholtz-Zentrum Geesthacht, Max-Plank-Str. 1, D-21502 Geesthacht (Germany); Brokmeier, H.-G. [Helmholtz-Zentrum Geesthacht, Max-Plank-Str. 1, D-21502 Geesthacht (Germany); Institute of Materials Science and Engineering, Clausthal University of Technology, Agricolastr. 6, D-38678 Clausthal-Zellerfeld (Germany); Zhong, Z.Y.; Al-Hamdany, N.; Salih, M.; Wagner, L. [Institute of Materials Science and Engineering, Clausthal University of Technology, Agricolastr. 6, D-38678 Clausthal-Zellerfeld (Germany); Schell, N. [Helmholtz-Zentrum Geesthacht, Max-Plank-Str. 1, D-21502 Geesthacht (Germany)
2014-01-31
Residual stress determination in engineering components from diffraction strain measurements needs reliable diffraction elastic constants (DECs). From this sense, in situ uniaxial tensile loading experiment was performed on alpha titanium alloy Ti–2.5Cu at the HEMS beamline at DESY by means of a monochromatic synchrotron X-ray diffraction. A comparison between measured (polycrystal) and calculated (single crystal) DECs using for example the Kröner model was presented and discussed. The results revealed that the measured DECs slightly differ from the calculated ones. Furthermore, changes in the lattice parameters a and c as well as c/a ratio during tensile loading were also investigated.
Energy Technology Data Exchange (ETDEWEB)
Gloaguen, D. [GeM, Institut de Recherche en Genie Civil et Mecanique, Universite de Nantes, Ecole Centrale de Nantes, CNRS UMR 6183, 37 Boulevard de l' Universite, BP 406, 44 602 Saint-Nazaire (France); Francois, M. [Laboratoire des Systemes Mecaniques et d' Ingenierie Simultanee (LASMIS FRE CNRS 2719), Universite de Technologie de Troyes, 12 Rue Marie Curie, BP 2060, 10010 Troyes cedex (France)
2006-06-15
A two-level homogenisation approach is applied to the micro-mechanical modelling of the elasto-plasticity of polycrystalline materials during various strain-path changes. The model is tested by simulating the development of intragranular strains during different complex loads. Mechanical tests measurements are used as a reference in order to validate the model. The anisotropy of plastic deformation in relation to the evolution of the dislocation structure is analysed. The results demonstrate the relevance of this approach for FCC polycrystals. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Cubic B-spline curve approximation by curve unclamping
Chen, Xiao-Diao; Ma, Weiyin; Paul, Jean-Claude
2010-01-01
International audience; A new approach for cubic B-spline curve approximation is presented. The method produces an approximation cubic B-spline curve tangent to a given curve at a set of selected positions, called tangent points, in a piecewise manner starting from a seed segment. A heuristic method is provided to select the tangent points. The first segment of the approximation cubic B-spline curve can be obtained using an inner point interpolation method, least-squares method or geometric H...
On q-power cycles in cubic graphs
DEFF Research Database (Denmark)
Bensmail, Julien
2017-01-01
In the context of a conjecture of Erdos and Gyárfás, we consider, for any q ≥ 2, the existence of q-power cycles (i.e. with length a power of q) in cubic graphs. We exhibit constructions showing that, for every q ≥ 3, there exist arbitrarily large cubic graphs with no q-power cycles. Concerning...... the remaining case q = 2 (which corresponds to the conjecture of Erdos and Gyárfás), we show that there exist arbitrarily large cubic graphs whose only 2-power cycles have length 4 only, or 8 only....
On q-power cycles in cubic graphs
DEFF Research Database (Denmark)
Bensmail, Julien
2016-01-01
In the context of a conjecture of Erdos and Gyárfás, we consider, for any q ≥ 2, the existence of q-power cycles (i.e. with length a power of q) in cubic graphs. We exhibit constructions showing that, for every q ≥ 3, there exist arbitrarily large cubic graphs with no q-power cycles. Concerning...... the remaining case q = 2 (which corresponds to the conjecture of Erdos and Gyárfás), we show that there exist arbitrarily large cubic graphs whose only 2-power cycles have length 4 only, or 8 only....
The compressibility of cubic white and orthorhombic, rhombohedral, and simple cubic black phosphorus
Energy Technology Data Exchange (ETDEWEB)
Clark, Simon M; Zaug, Joseph
2010-03-10
The effect of pressure on the crystal structure of white phosphorus has been studied up to 22.4 GPa. The ?alpha phase was found to transform into the alpha' phase at 0.87 +- 0.04 GPa with a volume change of 0.1 +- 0.3 cc/mol. A fit of a second order Birch- Murnaghan equation to the data gave Vo = 16.94 ? 0.08 cc/mol and Ko = 6.7 +- 0.5 GPa for the alpha phase and Vo = 16.4 +- 0.1 cc/mol and Ko = 9.1 +- 0.3 GPa for the alpha' phase. The alpha' phase was found to transform to the A17 phase of black phosphorus at 2.68 +- 0.34 GPa and then with increasing pressure to the A7 and then simple cubic phase of black phosphorus. A fit of a second order Birch-Murnaghan equation to our data combined with previous measurements gave Vo = 11.43 +- 0.05 cc/mol and Ko = 34.7 +- 0.5 GPa for the A17 phase, Vo = 9.62 +- 0.01 cc/mol and Ko = 65.0 +- 0.6 GPa for the A7 phase and , Vo = 9.23 +- 0.01 cc/mol and Ko = 72.5 +- 0.3 GPa for the simple cubic phase.
Cubic Gallium Nitride on Micropatterned Si (001) for Longer Wavelength LEDs
Energy Technology Data Exchange (ETDEWEB)
Durniak, Mark T. [Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Materials Science and Engineering; Chaudhuri, Anabil [Univ. of New Mexico, Albuquerque, NM (United States). Center for High Technology Materials; Smith, Michael L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Advanced Material Sciences; Allerman, Andrew A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Advanced Material Sciences; Lee, S. C. [Univ. of New Mexico, Albuquerque, NM (United States). Center for High Technology Materials; Brueck, S. R. J. [Univ. of New Mexico, Albuquerque, NM (United States). Center for High Technology Materials; Wetzel, Christian [Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Physics, Applied Physics, and Astronomy and Dept. of Materials Science and Engineering
2016-03-01
GaInN/GaN heterostructures of cubic phase have the potential to overcome the limitations of wurtzite structures commonly used for light emitting and laser diodes. Wurtzite GaInN suffers from large internal polarization fields, which force design compromises ( 0001 ) towards ultra-narrow quantum wells and reduce recombination volume and efficiency. Cubic GaInN microstripes grown at Rensselaer Polytechnic Institute by metal organic vapor phase epitaxy on micropatterned Si , with {111} v-grooves oriented along Si ( 001 ) , offer a system free of internal polarization fields, wider quantum wells, and smaller <00$\\bar1$> bandgap energy. We prepared 6 and 9 nm Ga _{x} In _{1-x} N/GaN single quantum well structures with peak wavelength ranges from 520 to 570 nm with photons predominately polarized perpendicular to the grooves. We estimate a cubic InN composition range of 0 < x < 0.5 and an upper limit of the internal quantum efficiency of 50%. Stripe geometry and polarization may be suitable for mode confinement and reduced threshold stimulated emission.
Structure and Luminescence Properties of Eu3+-Doped Cubic Mesoporous Silica Thin Films
Directory of Open Access Journals (Sweden)
Lu Qingshan
2010-01-01
Full Text Available Abstract Eu3+ ions-doped cubic mesoporous silica thin films with a thickness of about 205 nm were prepared on silicon and glass substrates using triblock copolymer as a structure-directing agent using sol–gel spin-coating and calcination processes. X-ray diffraction and transmission electron microscopy analysis show that the mesoporous silica thin films have a highly ordered body-centered cubic mesoporous structure. High Eu3+ ion loading and high temperature calcination do not destroy the ordered cubic mesoporous structure of the mesoporous silica thin films. Photoluminescence spectra show two characteristic emission peaks corresponding to the transitions of5D0-7F1 and 5D0-7F2 of Eu3+ ions located in low symmetry sites in mesoporous silica thin films. With the Eu/Si molar ratio increasing to 3.41%, the luminescence intensity of the Eu3+ ions-doped mesoporous silica thin films increases linearly with increasing Eu3+ concentration.
Structure and luminescence properties of eu3+-doped cubic mesoporous silica thin films.
Lu, Qingshan; Wang, Zhongying; Wang, Peiyu; Li, Jiangong
2010-02-11
Eu3+ ions-doped cubic mesoporous silica thin films with a thickness of about 205 nm were prepared on silicon and glass substrates using triblock copolymer as a structure-directing agent using sol-gel spin-coating and calcination processes. X-ray diffraction and transmission electron microscopy analysis show that the mesoporous silica thin films have a highly ordered body-centered cubic mesoporous structure. High Eu3+ ion loading and high temperature calcination do not destroy the ordered cubic mesoporous structure of the mesoporous silica thin films. Photoluminescence spectra show two characteristic emission peaks corresponding to the transitions of5D0-7F1 and 5D0-7F2 of Eu3+ ions located in low symmetry sites in mesoporous silica thin films. With the Eu/Si molar ratio increasing to 3.41%, the luminescence intensity of the Eu3+ ions-doped mesoporous silica thin films increases linearly with increasing Eu3+ concentration.
Global infinite energy solutions for the cubic wave equation
Burq, N.; L. Thomann; Tzvetkov, N.
2012-01-01
International audience; We prove the existence of infinite energy global solutions of the cubic wave equation in dimension greater than 3. The data is a typical element on the support of suitable probability measures.
The Coulombic Lattice Potential of Ionic Compounds: The Cubic Perovskites.
Francisco, E.; And Others
1988-01-01
Presents coulombic models representing the particles of a system by point charges interacting through Coulomb's law to explain coulombic lattice potential. Uses rubidium manganese trifluoride as an example of cubic perovskite structure. Discusses the effects on cluster properties. (CW)
Spinning solitons in cubic-quintic nonlinear media
Indian Academy of Sciences (India)
Lucian-Cornel Crasovan; Boris A Malomed; Dumitru Mihalache
2001-11-01
We review recent theoretical results concerning the existence, stability and unique features of families of bright vortex solitons (doughnuts, or ‘spinning’ solitons) in both conservative and dissipative cubic-quintic nonlinear media.
Stress Intensity of Antiplane Conjugate Cracks in Cubic Quasicrystal
Institute of Scientific and Technical Information of China (English)
ZHANG Lei
2008-01-01
Based on the theory of Muskhelishvili, the general solutions for stress and strain of conjugate cracks in cubic quasicrystal are obtained, with which the stress intensity factors of cubic quasicrystal at crack tips and the stress distribution functions of phonon and phason fields are given. The results show that though phason field is coupled with phonon field by constitutive equations, the stress intensity factors are not coupled with any other factors.
Optical studies of cubic III-nitride structures
Powell, Ross E L
2014-01-01
The properties of cubic nitrides grown by molecular beam epitaxy (MBE) on GaAs (001) have been studied using optical and electrical techniques. The aim of these studies was the improvement of the growth techniques in order to improve the quality of grown nitrides intended for bulk substrate and optoelectronic device applications. We have also characterised hexagonal nanocolumn structures incorporating indium. Firstly, bulk films of cubic AlxGa1-xN with aluminium fractions (x) spanning the ...
Rapid hydrothermal route to synthesize cubic-phase gadolinium oxide nanorods
Indian Academy of Sciences (India)
Samiran Hazarika; Nibedita Paul; Dambarudhar Mohanta
2014-06-01
An inexpensive fabrication route and growth mechanism is being reported for obtaining quality gadolinium oxide (Gd2O3) nanoscale rods. The elongated nanoscale systems, as produced via a hydrothermal process, were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), optical absorption spectroscopy, photoluminescence (PL) spectroscopy, Raman spectroscopy and magnetic hysteresis measurements. XRD patterns of the nanorods, as-prepared from independent precursors of different pH, depict a cubic crystal phase and an average crystallite size of 5-6.5 nm. As revealed from HRTEM micrographs, diameter of the nanorods prepared at pH = 13.3 (∼ 7nm) was much smaller than the rods prepared at pH = 10.8 (∼ 19nm). However, the aspect ratio was more than double in the former case than the latter case. PL response was found to be dominated by defect mediated emissions, whereas Raman spectrum of a given specimen (pH = 10.8) has revealed characteristic g + g modes of cubic phase of Gd2O3 nanorods, apart from other independent modes. Furthermore, ∼ plot of the nanorod system (pH = 10.8) exhibited slight departure from the ideal superparamagnetic behaviour, with low remanence and coercive field values. The exploitation of one-dimensional Gd2O3 nanorods have immense potential in the production of advanced contrast agents, smart drives and also in making novel ferrofluids of technological relevance.
Face-Centred-Cubic Artificial Opal Embedded with CdS Quantum Dots
Institute of Scientific and Technical Information of China (English)
徐岭; 李明海; 张宇; 马懿; 徐骏; 黄信凡; 陈坤基
2002-01-01
Highly monodispersed colloidal silica spheres in sub-micrometre size with distribution standard deviation less than 5% were synthesized by a chemical method. Using the self-crystallization of the silica spheres, we successfully obtained the three-dimensional close-packed face-centred-cubic silica matrices and artificial opals. Then,a colloidal photonic crystal embedded with CdS quantum dots (QDs) was also chemically prepared by using artificial opals as a template. A reflection spectra study reveals that both artificial opals with and without CdS QDs possess (111) directional photonic bandgap features.
Spinor bose gases in cubic optical lattice
Energy Technology Data Exchange (ETDEWEB)
Mobarak, Mohamed Saidan Sayed Mohamed
2014-01-27
In recent years the quantum simulation of condensed-matter physics problems has resulted from exciting experimental progress in the realm of ultracold atoms and molecules in optical lattices. In this thesis we analyze theoretically a spinor Bose gas loaded into a three-dimensional cubic optical lattice. In order to account for different superfluid phases of spin-1 bosons with a linear Zeeman effect, we work out a Ginzburg-Landau theory for the underlying spin-1 Bose-Hubbard model. To this end we add artificial symmetry-breaking currents to the spin-1 Bose-Hubbard Hamiltonian in order to break the global U (1) symmetry. With this we determine a diagrammatic expansion of the grand-canonical free energy up to fourth order in the symmetry-breaking currents and up to the leading non-trivial order in the hopping strength which is of first order. As a cross-check we demonstrate that the resulting grand-canonical free energy allows to recover the mean-field theory. Applying a Legendre transformation to the grand-canonical free energy, where the symmetry-breaking currents are transformed to order parameters, we obtain the effective Ginzburg-Landau action. With this we calculate in detail at zero temperature the Mott insulator-superfluid quantum phase boundary as well as condensate and particle number density in the superfluid phase. We find that both mean-field and Ginzburg-Landau theory yield the same quantum phase transition between the Mott insulator and superfluid phases, but the range of validity of the mean-field theory turns out to be smaller than that of the Ginzburg-Landau theory. Due to this finding we expect that the Ginzburg-Landau theory gives better results for the superfluid phase and, thus, we restrict ourselves to extremize only the effective Ginzburg-Landau action with respect to the order parameters. Without external magnetic field the superfluid phase is a polar (ferromagnetic) state for anti-ferromagnetic (ferromagnetic) interactions, i.e. only the
Ultrasound-assisted microwave preparation of Ag-doped CdS nanoparticles.
Ma, Jun; Tai, Guo'an; Guo, Wanlin
2010-03-01
Ag-doped CdS nanoparticles were synthesized by an ultrasound-assisted microwave synthesis method. The X-ray diffraction patterns reveal a structural evolution from cubic to hexagonal with increasing molar ratios of Ag(+)/Cd(2+) from 0% to 5%. It shows that the Ag-doped hexagonal CdS nanoparticles are polycrystal. The X-ray photoelectron spectroscopy of the CdS nanoparticles doping with 5% Ag(+) shows that the doped Ag in CdS is metallic. Simultaneously, the characteristic Raman peaks of the CdS nanoparticles enhance with increasing Ag(+) concentrations. The photocatalytic activity of different Ag-doped samples show a reasonable change due to different ratios of Ag which doped into CdS. Copyright 2009 Elsevier B.V. All rights reserved.
Synthesis, characterization and processing of cubic iron pyrite nanocrystals in a photovoltaic cell
Energy Technology Data Exchange (ETDEWEB)
Alam Khan, M., E-mail: alamkhan77@gmail.com; Sarker, J.C.; Lee, Seunyong; Mangham, Scott C.; Manasreh, M.O.
2014-12-15
Cubic iron pyrite (fool's gold) nanocrystals with an average diameter of ∼60 nm were grown in an oleylamine ligand which acts as a solvent and surfactant without the utilization of alkyl phosphine and phosphonic acids at 230 °C in a Schlenk flask. For the first time photoluminescence properties of such cubic nanocrystals were analyzed at 77 K, showing band gaps of 1.71 eV. However, UV–Vis spectra shows a band gap of 1.41 eV for the same nanocrystals, close to the direct band gap (1.38 eV) of reported pyrite materials. The discrepancy of 0.3 eV in absorption (UV–Vis) and emission spectra (PL) are attributed to the phonon coupling (stokes shift). The prepared cubic nanocrystals were well suited for an inexpensive thin film solar cells and further processed and spin casted with a synthesized CdSe quantum dots in chloroform solvent as a bulk-heterojunction (BHJ) solar cell in order to get photovoltaic responses in real devices. We successfully report here an efficiency of 0.5% with the J{sub SC} of 3.7 mA/cm{sup −2} and V{sub OC} of 0.16 mV with a cell structure of ITO/PEDOT:PSS/FeS{sub 2}:CdSe/Au. The morphology and optoelectronic properties are elucidated by SEM, TEM, TEM-EDS, XRD, micro-Raman spectra, IV curve and micro-PL techniques. - Highlights: • Excellent cubic iron pyrite nanocrystals are synthesized by using an oleylamine ligand. • First time PL spectra were used to measure band gaps of such colloidal cubic nanocrytsals. • Pyrite ink was made in suitable solvent to fabricate practical devices. • A successful 0.5% efficiency is reported in bulk-heterojunction cell with CdSe QDs.
A new hypercube variant: Fractal Cubic Network Graph
Directory of Open Access Journals (Sweden)
Ali Karci
2015-03-01
Full Text Available Hypercube is a popular and more attractive interconnection networks. The attractive properties of hypercube caused the derivation of more variants of hypercube. In this paper, we have proposed two variants of hypercube which was called as “Fractal Cubic Network Graphs”, and we have investigated the Hamiltonian-like properties of Fractal Cubic Network Graphs FCNGr(n. Firstly, Fractal Cubic Network Graphs FCNGr(n are defined by a fractal structure. Further, we show the construction and characteristics analyses of FCNGr(n where r=1 or r=2. Therefore, FCNGr(n is a Hamiltonian graph which is obtained by using Gray Code for r=2 and FCNG1(n is not a Hamiltonian Graph. Furthermore, we have obtained a recursive algorithm which is used to label the nodes of FCNG2(n. Finally, we get routing algorithms on FCNG2(n by utilizing routing algorithms on the hypercubes.
Ferromagnetic Ground States in Face-Centered Cubic Hubbard Clusters
Souza, T. X. R.; Macedo, C. A.
2016-01-01
In this study, the ground state energies of face-centered cubic Hubbard clusters are analyzed using the Lanczos method. Examination of the ground state energy as a function of the number of particle per site n showed an energy minimum for face-centered cubic structures. This energy minimum decreased in n with increasing coulombic interaction parameter U. We found that the ground state energy had a minimum at n = 0.6, when U = 3W, where W denotes the non-interacting energy bandwidth and the face-centered cubic structure was ferromagnetic. These results, when compared with the properties of nickel, shows strong similarity with other finite temperature analyses in the literature and supports the Hirsh’s conjecture that the interatomic direct exchange interaction dominates in driving the system into a ferromagnetic phase. PMID:27583653
Superconductivity in cubic noncentrosymmetric PdBiSe Crystal
Joshi, B.; Thamizhavel, A.; Ramakrishnan, S.
2015-03-01
Mixing of spin singlet and spin triplet superconducting pairing state is expected in noncentrosymmetric superconductors (NCS) due to the inherent presence of Rashba-type antisymmetric spin-orbit coupling. Unlike low symmetry (tetragonal or monoclinic) NCS, parity is isotropicaly broken in space for cubic NCS and can additionally lead to the coexistence of magnetic and superconducting state under certain conditions. Motivated with such enriched possibility of unconventional superconducting phases in cubic NCS we are reporting successful formation of single crystalline cubic noncentrosymmetric PdBiSe with lattice parameter a = 6.4316 Å and space group P21 3 (space group no. 198) which undergoes to superconducting transition state below 1.8 K as measured by electrical transport and AC susceptibility measurements. Significant strength of Rashba-type antisymmetric spin-orbit coupling can be expected for PdBiSe due to the presence of high Z (atomic number) elements consequently making it potential candidate for unconventional superconductivity.
Cubic interactions of Maxwell-like higher spins
Francia, Dario; Mkrtchyan, Karapet
2016-01-01
We study the cubic vertices for Maxwell-like higher-spins in flat space. Reducibility of their free spectra implies that a single cubic vertex involving any three fields subsumes a number of couplings among different particles of various spins. The resulting vertices do not involve traces of the fields and in this sense are simpler than their Fronsdal counterparts. We propose an extension of both the free theory and of its cubic deformation to a more general class of partially reducible systems, that one can obtain from the original theory upon imposing trace constraints of various orders. The key to our results is a version of the Noether procedure allowing to systematically account for the deformations of the transversality conditions to be imposed on the gauge parameters at the free level.
Extended temperature dependence of elastic constants in cubic crystals.
Telichko, A V; Sorokin, B P
2015-08-01
To extend the theory of the temperature dependence of the elastic constants in cubic crystals beyond the second- and third-order elastic constants, the fourth-order elastic constants, as well as the non-linearity in the thermal expansion temperature dependence, have been taken into account. Theoretical results were represented as temperature functions of the effective elastic constants and compared with experimental data for a number of cubic crystals, such as alkali metal halides, and elements gold and silver. The relations obtained give a more accurate description of the experimental temperature dependences of second-order elastic constants for a number of cubic crystals, including deviations from linear behavior. A good agreement between theoretical estimates and experimental data has been observed.
Tetragonal and cubic zirconia multilayered ceramic constructs created by EPD.
Mochales, Carolina; Frank, Stefan; Zehbe, Rolf; Traykova, Tania; Fleckenstein, Christine; Maerten, Anke; Fleck, Claudia; Mueller, Wolf-Dieter
2013-02-14
The interest in electrophoretic deposition (EPD) for nanomaterials and ceramics production has widely increased due to the versatility of this technique to effectively combine different materials in unique shapes and structures. We successfully established an EPD layering process with submicrometer sized powders of Y-TZP with different mol percentages of yttrium oxide (3 and 8%) and produced multilayers of alternating tetragonal and cubic phases with a clearly defined interface. The rationale behind the design of these multilayer constructs was to optimize the properties of the final ceramic by combining the high mechanical toughness of the tetragonal phase of zirconia together with the high ionic conductivity of its cubic phase. In this work, a preliminary study of the mechanical properties of these constructs proved the good mechanical integrity of the multilayered constructs obtained as well as crack deflection in the interface between tetragonal and cubic zirconia layers.
Body-centered-cubic Ni and its magnetic properties.
Tian, C S; Qian, D; Wu, D; He, R H; Wu, Y Z; Tang, W X; Yin, L F; Shi, Y S; Dong, G S; Jin, X F; Jiang, X M; Liu, F Q; Qian, H J; Sun, K; Wang, L M; Rossi, G; Qiu, Z Q; Shi, J
2005-04-08
The body-centered-cubic (bcc) phase of Ni, which does not exist in nature, has been achieved as a thin film on GaAs(001) at 170 K via molecular beam epitaxy. The bcc Ni is ferromagnetic with a Curie temperature of 456 K and possesses a magnetic moment of 0.52+/-0.08 micro(B)/atom. The cubic magnetocrystalline anisotropy of bcc Ni is determined to be +4.0x10(5) ergs x cm(-3), as opposed to -5.7x10(4) ergs x cm(-3) for the naturally occurring face-centered-cubic (fcc) Ni. This sharp contrast in the magnetic anisotropy is attributed to the different electronic band structures between bcc Ni and fcc Ni, which are determined using angle-resolved photoemission with synchrotron radiation.
Hardness and thermal stability of cubic silicon nitride
DEFF Research Database (Denmark)
Jiang, Jianzhong; Kragh, Flemming; Frost, D. J.
2001-01-01
The hardness and thermal stability of cubic spinel silicon nitride (c-Si3N4), synthesized under high-pressure and high-temperature conditions, have been studied by microindentation measurements, and x-ray powder diffraction and scanning electron microscopy, respectively The phase at ambient...... temperature has an average hardness of 35.31 GPa, slightly larger than SiO2 stishovite, which is often referred to as the third hardest material after diamond and cubic boron nitride. The cubic phase is stable up to 1673 K in air. At 1873 K, alpha -and beta -Si3N4 phases are observed, indicating a phase...... transformation sequence of c-to-alpha -to-beta -Si3N4 phases....
Image interpolation by two-dimensional parametric cubic convolution.
Shi, Jiazheng; Reichenbach, Stephen E
2006-07-01
Cubic convolution is a popular method for image interpolation. Traditionally, the piecewise-cubic kernel has been derived in one dimension with one parameter and applied to two-dimensional (2-D) images in a separable fashion. However, images typically are statistically nonseparable, which motivates this investigation of nonseparable cubic convolution. This paper derives two new nonseparable, 2-D cubic-convolution kernels. The first kernel, with three parameters (designated 2D-3PCC), is the most general 2-D, piecewise-cubic interpolator defined on [-2, 2] x [-2, 2] with constraints for biaxial symmetry, diagonal (or 90 degrees rotational) symmetry, continuity, and smoothness. The second kernel, with five parameters (designated 2D-5PCC), relaxes the constraint of diagonal symmetry, based on the observation that many images have rotationally asymmetric statistical properties. This paper also develops a closed-form solution for determining the optimal parameter values for parametric cubic-convolution kernels with respect to ensembles of scenes characterized by autocorrelation (or power spectrum). This solution establishes a practical foundation for adaptive interpolation based on local autocorrelation estimates. Quantitative fidelity analyses and visual experiments indicate that these new methods can outperform several popular interpolation methods. An analysis of the error budgets for reconstruction error associated with blurring and aliasing illustrates that the methods improve interpolation fidelity for images with aliased components. For images with little or no aliasing, the methods yield results similar to other popular methods. Both 2D-3PCC and 2D-5PCC are low-order polynomials with small spatial support and so are easy to implement and efficient to apply.
Synthesis, characterization and catalytic evaluation of cubic ordered mesoporous iron-silicon oxides
Energy Technology Data Exchange (ETDEWEB)
Martins, T.S., E-mail: tsmartins@unifesp.br [Departamento de Ciencias Exatas e da Terra, Universidade Federal de Sao Paulo, Rua Prof. Artur Riedel 275, 09972-270 Diadema, Sao Paulo (Brazil); Mahmoud, A.; Cides da Silva, L.C. [Instituto de Quimica, Universidade de Sao Paulo, 05508-900 Sao Paulo (Brazil); Cosentino, I.C. [IPEN, Av. Prof. Lineu Prestes 2242, Cidade Universitaria, 05508-900 Sao Paulo (Brazil); Tabacniks, M.H. [Instituto de Fisica, Universidade de Sao Paulo 66318, 05315-970 Sao Paulo (Brazil); Matos, J.R. [Instituto de Quimica, Universidade de Sao Paulo, 05508-900 Sao Paulo (Brazil); Freire, R.S. [CEPEMA/USP, Centro de Capacitacao e Pesquisa em Meio Ambiente, Cubatao/SP (Brazil); Instituto de Quimica, Universidade de Sao Paulo, 05508-900 Sao Paulo (Brazil); Fantini, M.C.A. [Instituto de Fisica, Universidade de Sao Paulo 66318, 05315-970 Sao Paulo (Brazil)
2010-11-01
Iron was successfully incorporated in FDU-1 type cubic ordered mesoporous silica by a simple direct synthesis route. The (Fe/FDU-1) samples were characterized by Rutherford back-scattering spectrometry (RBS), small angle X-ray scattering (SAXS), N{sub 2} sorption isotherm, X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). The resulting material presented an iron content of about 5%. Prepared at the usual acid pH of -0.3, the composite was mostly formed by amorphous silica and hematite with a quantity of Fe{sup 2+} present in the structure. The samples prepared with adjusted pH values (2 and 3.5) were amorphous. The samples' average pore diameter was around 12.0 nm and BET specific surface area was of 680 m{sup 2} g{sup -1}. Although the iron-incorporated material presented larger lattice parameter, about 25 nm compared to pure FDU-1, the Fe/FDU-1 composite still maintained its cubic ordered fcc mesoporous structure before and after the template removal at 540 deg. C. The catalytic performance of Fe/FDU-1 was investigated in the catalytic oxidation of Black Remazol B dye using a catalytic ozonation process. The results indicated that Fe/FDU-1 prepared at the usual acid pH exhibited high catalytic activity in the mineralization of this pollutant when compared to the pure FDU-1, Fe{sub 2}O{sub 3} and Fe/FDU-1 prepared with higher pH of 2 and 3.5.
Higher-spin Interactions from CFT: The Complete Cubic Couplings
Sleight, Charlotte
2016-01-01
In this letter we provide a complete holographic reconstruction of the cubic couplings in the minimal bosonic higher-spin theory in AdS$_{d+1}$. For this purpose we also determine the OPE coefficients of all single-trace conserved currents in the $d$-dimensional free scalar $O\\left(N\\right)$ vector model, and compute the tree-level three-point Witten diagram amplitudes for a generic cubic interaction of higher-spin gauge fields in the metric-like formulation.
Classifying Cubic Edge-Transitive Graphs of Order 8
Indian Academy of Sciences (India)
Mehdi Alaeiyan; M K Hosseinipoor
2009-11-01
A simple undirected graph is said to be semisymmetric if it is regular and edge-transitive but not vertex-transitive. Let be a prime. It was shown by Folkman (J. Combin. Theory 3(1967) 215--232) that a regular edge-transitive graph of order 2 or 22 is necessarily vertex-transitive. In this paper, an extension of his result in the case of cubic graphs is given. It is proved that, every cubic edge-transitive graph of order 8 is symmetric, and then all such graphs are classified.
Possible form of multi-polar interaction in cubic lattice
Energy Technology Data Exchange (ETDEWEB)
Sakai, Osamu; Shiina, Ryousuke; Shiba, Hiroyuki
2003-05-01
The invariant form of interaction between multi-poles, including the octupole, is studied for the simple cubic (SC), body centered and face centered cubic lattices. The coupling terms can be arranged in a way similar to that of the hopping matrix between the LCAO's. A table for SC by Shiina et al. (J. Phys. Soc. Japan 66 (1997) 1741) is generalized for the general wave number case of the three types of lattice. Recent experimental result of TmTe is thereby analyzed. The development of the ferromagnetic moment below the anti-ferromagnetic transition under the anti-ferro quadrupolar order phase is discussed in this connection.
Possible form of multi-polar interaction in cubic lattice
Sakai, Osamu; Shiina, Ryousuke; Shiba, Hiroyuki
2003-05-01
The invariant form of interaction between multi-poles, including the octupole, is studied for the simple cubic (SC), body centered and face centered cubic lattices. The coupling terms can be arranged in a way similar to that of the hopping matrix between the LCAO's. A table for SC by Shiina et al. (J. Phys. Soc. Japan 66 (1997) 1741) is generalized for the general wave number case of the three types of lattice. Recent experimental result of TmTe is thereby analyzed. The development of the ferromagnetic moment below the anti-ferromagnetic transition under the anti-ferro quadrupolar order phase is discussed in this connection.
Counting perfect matchings of cubic graphs in the geometric dual
Jiménez, Andrea
2010-01-01
Lov\\'asz and Plummer conjectured, in the mid 1970's, that every cubic graph G with no cutedge has an exponential in |V(G)| number of perfect matchings. In this work we show that every cubic planar graph G whose geometric dual graph is a stack triangulation has at least 3 times the golden ratio to |V(G)|/72 distinct perfect matchings. Our work builds on a novel approach relating Lov\\'asz and Plummer's conjecture and the number of so called groundstates of the widely studied Ising model from statistical physics.
Elastic interaction of point defects in crystals with cubic symmetry
Kuz'michev, S. V.; Kukushkin, S. A.; Osipov, A. V.
2013-07-01
The energy of elastic mechanical interaction between point defects in cubic crystals is analyzed numerically. The finite-element complex ANSYS is used to investigate the character of interaction between point defects depending on their location along the crystallographic directions , , and on the distance from the free boundary of the crystal. The numerical results are compared with the results of analytic computations of the energy of interaction between two point defects in an infinite anisotropic medium with cubic symmetry. The interaction between compressible and incompressible defects of general type is studied. Conditions for onset of elastic attraction between the defects, which leads to general relaxation of the crystal elastic energy, are obtained.
Cubic surfaces and their invariants: Some memories of Raymond Stora
Directory of Open Access Journals (Sweden)
Michel Bauer
2016-11-01
I then turn to the study of the family of cubic surfaces. They depend on 20 parameters, and the action of the 15 parameter group SL4(C splits the family in orbits depending on 5 parameters. This takes us into the realm of (geometric invariant theory. I review briefly the classical theorems on the structure of the ring of polynomial invariants and illustrate its many facets by looking at a simple example, before turning to the already involved case of cubic surfaces. The invariant ring was described in the 19th century. I show how to retrieve this description via counting/generating functions and character formulae.
Huber, S.P.; Medvedev, V.V.; Meyer-Ilse, J.; Gullikson, E.; Padavala, B.; Edgar, J.H.; Sturm, J.M.; Kruijs, van de R.W.E.; Prendergast, D.; Bijkerk, F.
2016-01-01
The transmission of cubic boron phosphide (c-BP) thin films, prepared by chemical vapor deposition (CVD), was evaluated near the phosphorous L2,3 and boron K absorption edge. The c-BP films were analyzed with transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray ab
Phase diagrams and synthesis of cubic boron nitride
Turkevich, V Z
2002-01-01
On the basis of phase equilibria, the lowest temperatures, T sub m sub i sub n , above which at high pressures cubic boron nitride crystallization from melt solution is allowable in terms of thermodynamics have been found for a number of systems that include boron nitride.
Interaction of dispersed cubic phases with blood components
DEFF Research Database (Denmark)
Bode, J C; Kuntsche, Judith; Funari, S S;
2013-01-01
The interaction of aqueous nanoparticle dispersions, e.g. based on monoolein/poloxamer 407, with blood components is an important topic concerning especially the parenteral way of administration. Therefore, the influence of human and porcine plasma on dispersed cubic phases was investigated...
Cubic surfaces and their invariants: Some memories of Raymond Stora
Bauer, Michel
2016-11-01
Cubic surfaces embedded in complex projective 3-space are a classical illustration of the use of old and new methods in algebraic geometry. Recently, they made their appearance in physics, and in particular aroused the interest of Raymond Stora, to the memory of whom these notes are dedicated, and to whom I'm very much indebted. Each smooth cubic surface has a rich geometric structure, which I review briefly, with emphasis on the 27 lines and the combinatorics of their intersections. Only elementary methods are used, relying on first order perturbation/deformation theory. I then turn to the study of the family of cubic surfaces. They depend on 20 parameters, and the action of the 15 parameter group SL4 (C) splits the family in orbits depending on 5 parameters. This takes us into the realm of (geometric) invariant theory. I review briefly the classical theorems on the structure of the ring of polynomial invariants and illustrate its many facets by looking at a simple example, before turning to the already involved case of cubic surfaces. The invariant ring was described in the 19th century. I show how to retrieve this description via counting/generating functions and character formulae.
Exact solutions for the cubic-quintic nonlinear Schroedinger equation
Energy Technology Data Exchange (ETDEWEB)
Zhu Jiamin [Department of Physics, Zhejiang Lishui University, Lishui 323000 (China)]. E-mail: zjm64@163.com; Ma Zhengyi [Department of Physics, Zhejiang Lishui University, Lishui 323000 (China); Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai 200072 (China)
2007-08-15
In this paper, the cubic-quintic nonlinear Schroedinger equation is solved through the extended elliptic sub-equation method. As a consequence, many types of exact travelling wave solutions are obtained which including bell and kink profile solitary wave solutions, triangular periodic wave solutions and singular solutions.
Combinatorics on Words in Symbolic Dynamics: the Antisymmetric Cubic Map
Institute of Scientific and Technical Information of China (English)
Wan Ji DAI; Kebo L(U); Jun WANG
2008-01-01
This paper is contributed to the combinatorial properties of the periodic kneading words of antisymmetric cubic maps defined on a interval.The least words of given lengths,the adjacency relations on the words of given lengths and the parity-alternative property in some sets of such words are established.
A Unified Approach to Teaching Quadratic and Cubic Equations.
Ward, A. J. B.
2003-01-01
Presents a simple method for teaching the algebraic solution of cubic equations via completion of the cube. Shows that this method is readily accepted by students already familiar with completion of the square as a method for quadratic equations. (Author/KHR)
Orientational phase transition in cubic liquid crystals with positional order
Pokrovsky, V.L.; Saidachmetov, P.A.
1988-01-01
An electric field can give rise to a shear deformation of a cubic liquid crystal with long-range positional order fixed by two plates. The critical value of the field does not depend on the size of the system and depends crucially on the orientation.
An effective packing density of binary cubic crystals
Eremin, I. E.; Eremina, V. V.; Sychev, M. S.; Moiseenko, V. G.
2015-04-01
The methodology of effective macroscopic calculation of numerical values of internuclear distances in binary crystals of a cubic crystal system is based on the use of coefficients of the structural packing density of the crystal lattice. The possibility of combining the reference data on the main physicochemical parameters of the substance is implemented by synthesis of the corresponding mathematical models.
Trapping of cubic ZnO nanocrystallites at ambient conditions
DEFF Research Database (Denmark)
Decremps, F.; Pellicer-Porres, J.; Datchi, F.
2002-01-01
Dense powder of nanocrystalline ZnO has been recovered at ambient conditions in the metastable cubic structure after a heat treatment at high pressure (15 GPa and 550 K). Combined x-ray diffraction (XRD) and x-ray absorption spectroscopy (XAS) experiments have been performed to probe both long-ra...
Specific heat of the simple-cubic Ising model
Feng, X.; Blöte, H.W.J.
2010-01-01
We provide an expression quantitatively describing the specific heat of the Ising model on the simple-cubic lattice in the critical region. This expression is based on finite-size scaling of numerical results obtained by means of a Monte Carlo method. It agrees satisfactorily with series expansions
Connecting the Dots Parametrically: An Alternative to Cubic Splines.
Hildebrand, Wilbur J.
1990-01-01
Discusses a method of cubic splines to determine a curve through a series of points and a second method for obtaining parametric equations for a smooth curve that passes through a sequence of points. Procedures for determining the curves and results of each of the methods are compared. (YP)
Cubic spline approximation techniques for parameter estimation in distributed systems
Banks, H. T.; Crowley, J. M.; Kunisch, K.
1983-01-01
Approximation schemes employing cubic splines in the context of a linear semigroup framework are developed for both parabolic and hyperbolic second-order partial differential equation parameter estimation problems. Convergence results are established for problems with linear and nonlinear systems, and a summary of numerical experiments with the techniques proposed is given.
Rheology of cubic particles suspended in a Newtonian fluid.
Cwalina, Colin D; Harrison, Kelsey J; Wagner, Norman J
2016-05-18
Many real-world industrial processes involve non-spherical particles suspended in a fluid medium. Knowledge of the flow behavior of these suspensions is essential for optimizing their transport properties and designing processing equipment. In the present work, we explore and report on the rheology of concentrated suspensions of cubic-shaped colloidal particles under steady and dynamic shear flow. These suspensions exhibit a rich non-Newtonian rheology that includes shear thickening and normal stress differences at high shear stresses. Scalings are proposed to connect the material properties of these suspensions of cubic particle to those measured for suspensions of spherical particles. Negative first normal stress differences indicate that lubrication hydrodynamic forces dominate the stress in the shear-thickened state. Accounting for the increased lubrication hydrodynamic interactions between the flat surfaces of the cubic particles allows for a quantitative comparison of the deviatoric stress in the shear-thickened state to that of spherical particles. New semi-empirical models for the viscosity and normal stress difference coefficients are presented for the shear-thickened state. The results of this study indicate that cubic particles offer new and unique opportunities to formulate colloidal dispersions for field-responsive materials.
Infinite Face Centered Cubic Network of Identical Resistors
Asad, J H
2012-01-01
The equivalent resistance between the origin and any other lattice site, in an infinite Face Centered Cubic network consisting from identical resistors, has been expressed rationally in terms of the known value and . The asymptotic behavior is investigated, and some calculated values for the equivalent resistance are presented.
Trace spaces in a pre-cubical complex
DEFF Research Database (Denmark)
Raussen, Martin
In directed algebraic topology, (spaces of) directed irreversible (d)-paths are studied from a topological and from a categorical point of view. Motivated by models for concurrent computation, we study in this paper spaces of d-paths in a pre-cubical complex. Such paths are equipped with a natural...
SUPERCONVERGENCE ANALYSIS FOR CUBIC TRIANGULAR ELEMENT OF THE FINITE ELEMENT
Institute of Scientific and Technical Information of China (English)
Qi-ding Zhu
2000-01-01
In this paper, we construct a projection interpolation for cubic triangular ele- ment by using othogonal expansion triangular method. We show two fundamental formulas of estimation on a special partion and obtain a superconvergence result of 1 -e order higher for the placement function and its tangential derivative on the third order Lobatto points and Gauss points on each edge of triangular element.
Integrability of Lotka-Volterra Planar Complex Cubic Systems
Dukarić, Maša; Giné, Jaume
In this paper, we study the Lotka-Volterra complex cubic systems. We obtain necessary conditions of integrability for these systems with some restriction on the parameters. The sufficiency is proved for all conditions, except one which remains open, using different methods.
Global Well-Posedness for Cubic NLS with Nonlinear Damping
Antonelli, Paolo
2010-11-04
We study the Cauchy problem for the cubic nonlinear Schrödinger equation, perturbed by (higher order) dissipative nonlinearities. We prove global in-time existence of solutions for general initial data in the energy space. In particular we treat the energy-critical case of a quintic dissipation in three space dimensions. © Taylor & Francis Group, LLC.
Formation and properties of reverse micellar cubic liquid crystals and derived emulsions.
Rodríguez-Abreu, Carlos; Shrestha, Lok Kumar; Varade, Dharmesh; Aramaki, Kenji; Maestro, Alicia; Quintela, Arturo López; Solans, Conxita
2007-10-23
The structure of the reverse micellar cubic (I2) liquid crystal and the adjacent micellar phase in amphiphilic block copolymer/water/oil systems has been studied by small-angle X-ray scattering (SAXS), rheometry, and differential scanning calorimetry (DSC). Upon addition of water to the copolymer/oil mixture, spherical micelles are formed and grow in size until a disorder-order transition takes place, which is related to a sudden increase in the viscosity and shear modulus. The transition is driven by the packing of the spherical micelles into a Fd3m cubic lattice. The single-phase I2 liquid crystals show gel-like behavior and elastic moduli higher than 104 Pa, as determined by oscillatory measurements. Further addition of water induces phase separation, and it is found that reverse water-in-oil emulsions with high internal phase ratio and stabilized by I2 liquid crystals can be prepared in the two-phase region. Contrary to liquid-liquid emulsions, both the elastic modulus and the viscosity decrease with the fraction of dispersed water, due to a decrease in the crystalline fraction in the sample, although the reverse emulsions remain gel-like even at high volume fractions of the dispersed phase. A temperature induced order-disorder transition can be detected by calorimetry and rheometry. Upon heating the I2 liquid crystals, two thermal events associated with small enthalpy values were detected: one endothermic, related to the "melting" of the liquid crystal, and the other exothermic, attributed to phase separation. The melting of the liquid crystal is associated with a sudden drop in viscosity and shear moduli. Results are relevant for understanding the formation of cubic-phase-based reverse emulsions and for their application as templates for the synthesis of structured materials.
2011-01-01
Introduction Li7La3Zr2O12 ( LLZO ) has recently become of high interest as a result of its potential as a solid state Li-ion conductor, because it has good...ionic conductivity (>10−4 S/cm) and is stable against lithium [1-8]. However, for the case of LLZO two phases exist; cubic and te- tragonal [1-9]. The...tetragonal phase. Thus, it is important to understand how to prepare the cubic phase. Several reports describe the synthesis and characterization of LLZO
Electro chemical Generation of Cubic Shap ed Nano Zn2SnO4 Photocatalysts
Institute of Scientific and Technical Information of China (English)
Chandrappa K Govindappa; Venkatesha T Venkatarangaiah; Sharifah B Abd Hamid
2013-01-01
In this contribution, an eﬃcient and simple two-step hybrid electrochemical-thermal route was developed for the synthesis of cubic shaped Zn2SnO4 (ZTO) nanoparticles using aqueous sodium bicarbonate (NaHCO3) and sodium stannate (Na2SnO3) electrolyte. The sacrificial Zn was used as anode and cathode in an undivided cell under galvanostatic mode at room temperature. The bath concentration and current den-sity were respectively varied from 30 to 120 mmol and 0.05 to 1.5 A/dm2. The electrochemically generated precursor was calcined for an hour at different range of temperature from 60 to 600℃. The crystallite sizes in the range of 24-53 nm were calculated based on Debye-Scherrer equation. Scanning electron microscope and transmission electron microscopy results reveal that all the particles have cubic morphology with diameter of 40-50 nm. The as-prepared ZTO samples showed higher catalytic activity towards the degradation of methylene blue (MB) dye, and 90% degradation was found for the sample calcined at 600℃, which is greater than that of commercial TiO2-P25 photocatalysts. The photodegradation eﬃciency of ZTO samples was found to be a function of exposure time and the dye solution pH value. These results indicate that the ZTO nanoparticles may be employed to remove dyes from wastewater.
Institute of Scientific and Technical Information of China (English)
孙元喜; 胡霞; 周谷珍
2007-01-01
The poly(crystal violet)film modified electrodes (PCVE)were prepared by cyclic voltammetry,electrocatalytic action of PCVE on Uric Acid(UA)and Dopamine(DA)had been studied in particular.The results have shown that the PCVE has a strong electrocatalytic action for UA and DA,and a strong power of resisting interfere of AA.Uric Acid and Dopamine can be measured in existence of 1 000 times AA.Combining PCVE with difference pulse Voltammetry(DPV),the linearity range of determining DA is 4.0×10-7 mol/L～2.5×10-5 mol/L.the determination limits reach up to 3.5×10-8 mol/L;the linearity range of determining UA is 5.0×10-7 mol/L～5.0×10-5 mol/L,the determination limits are 5.0×10-8 mol/L.The DA and UA can be measured at the same time.The results are similar by Using the same method with UA of Urine samples.%利用循环伏安法制备了聚结晶紫薄膜修饰电极(PCVE),详细研究了该修饰电极对生物分子多巴胺(DA)和尿酸(UA)的电催化作用.结果表明,PCVE对DA和UA具有较强的电催化作用,并且对抗坏血酸(AA)具有较强的抗干扰作用,允许高达1 000倍以上AA存在而不干扰痕量DA的测定.将PCVE结合差分脉冲伏安(DPV)技术,对DA的检测线性范围为4.0×10-7 mol/L～2.5×10-5 mol/L,检测限可达3.5×10-8 mol/L;对UA的检测线性范围为5.0×10-7 mol/L～5.0×10-5 mol/L,检测限达5.0×10-8 mol/L.利用该法可以对DA和UA进行同时测定,将该法用于尿液中尿酸的测定,取得满意结果.
Bulian, Christopher J.; Dye, Robert C.; Son, Steven F.; Jorgensen, Betty S.; Perry, W. Lee
2009-09-22
Tungsten trioxide hydrate (WO.sub.3.H.sub.2O) was prepared from a precursor solution of ammonium paratungstate in concentrated aqueous hydrochloric acid. The precursor solution was rapidly added to water, resulting in the crash precipitation of a yellow white powder identified as WO.sub.3.H.sub.2O nanosized platelets by x-ray diffraction and scanning electron microscopy. Annealing of the powder at 200.degree. C. provided cubic phase WO.sub.3 nanopowder, and at 400.degree. C. provided WO.sub.3 nanopowder as a mixture of monoclinic and orthorhombic phases.
Liu, Jie; Fan, Xiayue; Liu, Xiaorui; Song, Zhishuang; Deng, Yida; Han, Xiaopeng; Hu, Wenbin; Zhong, Cheng
2017-06-07
A new approach has been developed for in situ preparing cubic-shaped Pt particles with (100) preferential orientation on the surface of the conductive support by using a quick, one-step, and clean electrochemical method with periodic square-wave potential. The whole electrochemical deposition process is very quick (only 6 min is required to produce cubic Pt particles), without the use of particular capping agents. The shape and the surface structure of deposited Pt particles can be controlled by the lower and upper potential limits of the square-wave potential. For a frequency of 5 Hz and an upper potential limit of 1.0 V (vs saturated calomel electrode), as the lower potential limit decreases to the H adsorption potential region, the Pt deposits are changed from nearly spherical particles to cubic-shaped (100)-oriented Pt particles. High-resolution transmission electron microscopy and selected-area electron diffraction reveal that the formed cubic Pt particles are single-crystalline and enclosed by (100) facets. Cubic Pt particles exhibit characteristic H adsorption/desorption peaks corresponding to the (100) preferential orientation. Ge irreversible adsorption indicates that the fraction of wide Pt(100) surface domains is 47.8%. The electrocatalytic activities of different Pt particles are investigated by ammonia electro-oxidation, which is particularly sensitive to the amount of Pt(100) sites, especially larger (100) domains. The specific activity of cubic Pt particles is 3.6 times as high as that of polycrystalline spherical Pt particles, again confirming the (100) preferential orientation of Pt cubes. The formation of cubic-shaped Pt particles is related with the preferential electrochemical deposition and dissolution processes of Pt, which are coupled with the periodic desorption and adsorption processes of O-containing species and H adatoms.
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
The calculation procedure of the continuum mechanics of textured polycrystals (CMTP) method is reviewed to estimate calculating time with various yield functions (YFs). A so-called semi-quadratic YF is proposed to eliminate time-consuming numerical calculation and avoid the decrease of prediction precision. The reasonability of the new YF is proved by making the comparisons between predicted R-values and earing behaviour for some materials and the experimental results.
Cubic ideal ferromagnets at low temperature and weak magnetic field
Hofmann, Christoph P.
2017-04-01
The low-temperature series for the free energy density, pressure, magnetization and susceptibility of cubic ideal ferromagnets in weak external magnetic fields are discussed within the effective Lagrangian framework up to three loops. The structure of the simple, body-centered, and face-centered cubic lattice is taken into account explicitly. The expansion involves integer and half-integer powers of the temperature. The corresponding coefficients depend on the magnetic field and on low-energy effective constants that can be expressed in terms of microscopic quantities. Our formulas may also serve as efficiency or consistency check for other techniques like Green's function methods, where spurious terms in the low-temperature expansion have appeared. We explore the sign and magnitude of the spin-wave interaction in the pressure, magnetization and susceptibility, and emphasize that our effective field theory approach is fully systematic and rigorous.
Counting real cubics with passage/tangency conditions
Lanzat, Sergei
2010-01-01
We study the following question: given a set of seven points and an immersed curve in the real plane R^2, all in general position, how many real rational nodal plane cubics pass through these points and are tangent to this curve. We count each such cubic with a certain sign, and present an explicit formula for their algebraic number. This number is preserved under small regular homotopies of the curve, but jumps (in a well-controlled way) when in the process of homotopy we pass a certain singular discriminant. We discuss the relation of such enumerative problems with finite type invariants. Our approach is based on maps of configuration spaces and the intersection theory in the spirit of classical algebraic topology.
Reversible Nanoparticle Cubic Lattices in Blue Phase Liquid Crystals.
Gharbi, Mohamed Amine; Manet, Sabine; Lhermitte, Julien; Brown, Sarah; Milette, Jonathan; Toader, Violeta; Sutton, Mark; Reven, Linda
2016-03-22
Blue phases (BPs), a distinct class of liquid crystals (LCs) with 3D periodic ordering of double twist cylinders involving orthogonal helical director twists, have been theoretically studied as potential templates for tunable colloidal crystals. Here, we report the spontaneous formation of thermally reversible, cubic crystal nanoparticle (NP) assemblies in BPs. Gold NPs, functionalized to be highly miscible in cyanobiphenyl-based LCs, were dispersed in BP mixtures and characterized by polarized optical microscopy and synchrotron small-angle X-ray scattering (SAXS). The NPs assemble by selectively migrating to periodic strong trapping sites in the BP disclination lines. The NP lattice, remarkably robust given the small particle size (4.5 nm diameter), is commensurate with that of the BP matrix. At the BP I to BP II phase transition, the NP lattice reversibly switches between two different cubic structures. The simultaneous presence of two different symmetries in a single material presents an interesting opportunity to develop novel dynamic optical materials.
Highly Aminated Mesoporous Silica Nanoparticles with Cubic Pore Structure
Suteewong, Teeraporn
2011-01-19
Mesoporous silica with cubic symmetry has attracted interest from researchers for some time. Here, we present the room temperature synthesis of mesoporous silica nanoparticles possessing cubic Pm3n symmetry with very high molar ratios (>50%) of 3-aminopropyl triethoxysilane. The synthesis is robust allowing, for example, co-condensation of organic dyes without loss of structure. By means of pore expander molecules, the pore size can be enlarged from 2.7 to 5 nm, while particle size decreases. Adding pore expander and co-condensing fluorescent dyes in the same synthesis reduces average particle size further down to 100 nm. After PEGylation, such fluorescent aminated mesoporous silica nanoparticles are spontaneously taken up by cells as demonstrated by fluorescence microscopy.
The Piecewise Cubic Method (PCM) for computational fluid dynamics
Lee, Dongwook; Faller, Hugues; Reyes, Adam
2017-07-01
We present a new high-order finite volume reconstruction method for hyperbolic conservation laws. The method is based on a piecewise cubic polynomial which provides its solutions a fifth-order accuracy in space. The spatially reconstructed solutions are evolved in time with a fourth-order accuracy by tracing the characteristics of the cubic polynomials. As a result, our temporal update scheme provides a significantly simpler and computationally more efficient approach in achieving fourth order accuracy in time, relative to the comparable fourth-order Runge-Kutta method. We demonstrate that the solutions of PCM converges at fifth-order in solving 1D smooth flows described by hyperbolic conservation laws. We test the new scheme on a range of numerical experiments, including both gas dynamics and magnetohydrodynamics applications in multiple spatial dimensions.
The Piecewise Cubic Method (PCM) for Computational Fluid Dynamics
Lee, Dongwook; Reyes, Adam
2016-01-01
We present a new high-order finite volume reconstruction method for hyperbolic conservation laws. The method is based on a piecewise cubic polynomial which provides its solutions a fifth-order accuracy in space. The spatially reconstructed solutions are evolved in time with a fourth-order accuracy by tracing the characteristics of the cubic polynomials. As a result, our temporal update scheme provides a significantly simpler and computationally more efficient approach in achieving fourth order accuracy in time, relative to the comparable fourth-order Runge-Kutta method. We demonstrate that the solutions of PCM converges in fifth-order in solving 1D smooth flows described by hyperbolic conservation laws. We test the new scheme in a range of numerical experiments, including both gas dynamics and magnetohydrodynamics applications in multiple spatial dimensions.
Cubic Composite Sensor with Photodiodes for Tracking Solar Orientation
Directory of Open Access Journals (Sweden)
Yong-Nong Chang
2013-01-01
Full Text Available A cubic composite solar sensor with photo diode is proposed for tracking the relative solar orientation. The proposed solar sensor composes of five photodiode detectors which are placed on the front, rear, left, right, and horizontal facets in a cubic body, respectively. The solar detectors placed on five facets can detect solar power of different facets. Based on the geometric coordinate transformation principle, the relationship equations of solar light orientation between measured powers with respect to various facets can be conducted. As a result, the solar orientation can be precisely achieved without needing any assistance of electronic compass and extra orientation angle corrector. Eventually, the relative solar light orientation, the elevation angle, and azimuth angle of the solar light can be measured precisely.
Nonlinear optical imaging of defects in cubic silicon carbide epilayers.
Hristu, Radu; Stanciu, Stefan G; Tranca, Denis E; Matei, Alecs; Stanciu, George A
2014-06-11
Silicon carbide is one of the most promising materials for power electronic devices capable of operating at extreme conditions. The widespread application of silicon carbide power devices is however limited by the presence of structural defects in silicon carbide epilayers. Our experiment demonstrates that optical second harmonic generation imaging represents a viable solution for characterizing structural defects such as stacking faults, dislocations and double positioning boundaries in cubic silicon carbide layers. X-ray diffraction and optical second harmonic rotational anisotropy were used to confirm the growth of the cubic polytype, atomic force microscopy was used to support the identification of silicon carbide defects based on their distinct shape, while second harmonic generation microscopy revealed the detailed structure of the defects. Our results show that this fast and noninvasive investigation method can identify defects which appear during the crystal growth and can be used to certify areas within the silicon carbide epilayer that have optimal quality.
Global Sufficient Optimality Conditions for a Special Cubic Minimization Problem
Directory of Open Access Journals (Sweden)
Xiaomei Zhang
2012-01-01
Full Text Available We present some sufficient global optimality conditions for a special cubic minimization problem with box constraints or binary constraints by extending the global subdifferential approach proposed by V. Jeyakumar et al. (2006. The present conditions generalize the results developed in the work of V. Jeyakumar et al. where a quadratic minimization problem with box constraints or binary constraints was considered. In addition, a special diagonal matrix is constructed, which is used to provide a convenient method for justifying the proposed sufficient conditions. Then, the reformulation of the sufficient conditions follows. It is worth noting that this reformulation is also applicable to the quadratic minimization problem with box or binary constraints considered in the works of V. Jeyakumar et al. (2006 and Y. Wang et al. (2010. Finally some examples demonstrate that our optimality conditions can effectively be used for identifying global minimizers of the certain nonconvex cubic minimization problem.
Plasma simulation with the Differential Algebraic Cubic Interpolated Propagation scheme
Energy Technology Data Exchange (ETDEWEB)
Utsumi, Takayuki [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment
1998-03-01
A computer code based on the Differential Algebraic Cubic Interpolated Propagation scheme has been developed for the numerical solution of the Boltzmann equation for a one-dimensional plasma with immobile ions. The scheme advects the distribution function and its first derivatives in the phase space for one time step by using a numerical integration method for ordinary differential equations, and reconstructs the profile in phase space by using a cubic polynomial within a grid cell. The method gives stable and accurate results, and is efficient. It is successfully applied to a number of equations; the Vlasov equation, the Boltzmann equation with the Fokker-Planck or the Bhatnagar-Gross-Krook (BGK) collision term and the relativistic Vlasov equation. The method can be generalized in a straightforward way to treat cases such as problems with nonperiodic boundary conditions and higher dimensional problems. (author)
Quantum spectra and classical periodic orbit in the cubic billiard
Institute of Scientific and Technical Information of China (English)
Dehua Wang; Yongjiang Yu; Shenglu Lin
2006-01-01
Quantum billiards have attracted much interest in many fields. People have made a lot of researches on the two-dimensional (2D) billiard systems. Contrary to the 2D billiard, due to the complication of its classical periodic orbits, no one has studied the correspondence between the quantum spectra and the classical orbits of the three-dimensional (3D) billiards. Taking the cubic billiard as an example, using the periodic orbit theory, we find the periodic orbit of the cubic billiard and study the correspondence between the quantum spectra and the length of the classical orbits in 3D system. The Fourier transformed spectrum of this system has allowed direct comparison between peaks in such plot and the length of the periodic orbits, which verifies the correctness of the periodic orbit theory. This is another example showing that semiclassical method provides a bridge between quantum and classical mechanics.
Quantum Phase Transitions in Anti-ferromagnetic Planar Cubic Lattices
Wellard, C J; Wellard, Cameron; Orus, Roman
2004-01-01
Motivated by its relation to an NP-hard problem we analyze the ground state properties of anti-ferromagnetic Ising-spin networks in planar cubic lattices under the action of homogeneous transverse and longitudinal magnetic fields. We consider different instances of the cubic geometry and find a set of quantum phase transitions for each one of the systems, which we characterize by means of entanglement behavior and majorization theory. Entanglement scaling at the critical region is in agreement with results arising from conformal symmetry, therefore even the simplest planar systems can display very large amounts of quantum correlation. No conclusion can be made as to the scaling behavior of the minimum energy gap, with the data allowing equally good fits to exponential and power law decays. Analysis of entanglement and especially of majorization instead of the energy spectrum proves to be a good way of detecting quantum phase transitions in highly frustrated configurations.
Higher-Order Approximation of Cubic-Quintic Duffing Model
DEFF Research Database (Denmark)
Ganji, S. S.; Barari, Amin; Babazadeh, H.
2011-01-01
We apply an Artificial Parameter Lindstedt-Poincaré Method (APL-PM) to find improved approximate solutions for strongly nonlinear Duffing oscillations with cubic-quintic nonlinear restoring force. This approach yields simple linear algebraic equations instead of nonlinear algebraic equations...... without analytical solution which makes it a unique solution. It is demonstrated that this method works very well for the whole range of parameters in the case of the cubic-quintic oscillator, and excellent agreement of the approximate frequencies with the exact one has been observed and discussed....... Moreover, it is not limited to the small parameter such as in the classical perturbation method. Interestingly, this study revealed that the relative error percentage in the second-order approximate analytical period is less than 0.042% for the whole parameter values. In addition, we compared...
3D Medical Image Interpolation Based on Parametric Cubic Convolution
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
In the process of display, manipulation and analysis of biomedical image data, they usually need to be converted to data of isotropic discretization through the process of interpolation, while the cubic convolution interpolation is widely used due to its good tradeoff between computational cost and accuracy. In this paper, we present a whole concept for the 3D medical image interpolation based on cubic convolution, and the six methods, with the different sharp control parameter, which are formulated in details. Furthermore, we also give an objective comparison for these methods using data sets with the different slice spacing. Each slice in these data sets is estimated by each interpolation method and compared with the original slice using three measures: mean-squared difference, number of sites of disagreement, and largest difference. According to the experimental results, we present a recommendation for 3D medical images under the different situations in the end.
Experimental core electron density of cubic boron nitride
DEFF Research Database (Denmark)
Wahlberg, Nanna; Bindzus, Niels; Bjerg, Lasse
candidate because of its many similarities with diamond: bonding pattern in the extended network structure, hardness, and the quality of the crystallites.3 However, some degree ionic interaction is a part of the bonding in boron nitride, which is not present in diamond. By investigating the core density...... beyond multipolar modeling of the valence density. As was recently shown in a benchmark study of diamond by Bindzus et al.1 The next step is to investigate more complicated chemical bonding motives, to determine the effect of bonding on the core density. Cubic boron nitride2 lends itself as a perfect...... in boron nitride we may obtain a deeper understanding of the effect of bonding on the total density. We report here a thorough investigation of the charge density of cubic boron nitride with a detailed modelling of the inner atom charge density. By combining high resolution powder X-ray diffraction data...
Quadratic and Cubic Nonlinear Oscillators with Damping and Their Applications
Li, Jibin; Feng, Zhaosheng
We apply the qualitative theory of dynamical systems to study exact solutions and the dynamics of quadratic and cubic nonlinear oscillators with damping. Under certain parametric conditions, we also consider the van der Waals normal form, Chaffee-Infante equation, compound Burgers-KdV equation and Burgers-KdV equation for explicit representations of kink-profile wave solutions and unbounded traveling wave solutions.
The Number of Real Roots of a Cubic Equation
Kavinoky, Richard; Thoo, John B.
2008-01-01
To find the number of distinct real roots of the cubic equation (1) x[caret]3 + bx[caret]2 + cx + d = 0, we could attempt to solve the equation. Fortunately, it is easy to tell the number of distinct real roots of (1) without having to solve the equation. The key is the discriminant. The discriminant of (1) appears in Cardan's (or Cardano's) cubic…
Multiscale Modeling of Point and Line Defects in Cubic Lattices
2007-01-01
and discli- nations with finite micropolar elastoplasticity . Int. J. Plasticity. 22:210–256, 2006. 56. Menzel, A., and Steinmann, P., On the contin...Voyiadjis, G. Z., A finite strain plastic- damage model for high velocity impact using combined viscosity and gradient localization limiters: Part I...Theoretical for- mulation. Int. J. Damage Mech. 15:293–334, 2006. 58. Milstein, F., and Chantasiriwan, S,. Theoretical study of the response of 12 cubic
INTEGRABILITY AND LINEARIZABILITY FOR A CLASS OF CUBIC KOLMOGOROV SYSTEMS
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
The integrability and linearizability for a class of cubic Kolmogorov systems are studied. A recursive formula to compute the saddle quantities of the systems is deduced firstly, and integrable conditions for the systems are obtained. Then a recursive formula to compute the coefficients of the normal form for saddle points of the systems is also applied. Finally linearizable conditions of the origin for the systems are given. Both formulas to find necessary conditions are all linear and readily done using c...
Photonic Crystal Cavities in Cubic Polytype Silicon Carbide Films
Radulaski, Marina; Buckley, Sonia; Rundquist, Armand; Provine, J; Alassaad, Kassem; Ferro, Gabriel; Vučković, Jelena
2013-01-01
We present the design, fabrication, and characterization of high quality factor and small mode volume planar photonic crystal cavities from cubic (3C) thin films (thickness ~ 200 nm) of silicon carbide (SiC) grown epitaxially on a silicon substrate. We demonstrate cavity resonances across the telecommunications band, with wavelengths from 1250 - 1600 nm. Finally, we discuss possible applications in nonlinear optics, optical interconnects, and quantum information science.
Infinite Body Centered Cubic Network of Identical Resistors
Asad, J H
2013-01-01
We express the equivalent resistance between the origin and any other lattice site in an infinite Body Centered Cubic (BCC) network consisting of identical resistors each of resistance R rationally in terms of known values and . The equivalent resistance is then calculated. Finally, for large separation between the origin and the lattice site two asymptotic formulas for the resistance are presented and some numerical results with analysis are given.
Lipidic cubic phase injector facilitates membrane protein serial femtosecond crystallography.
Weierstall, Uwe; James, Daniel; Wang, Chong; White, Thomas A; Wang, Dingjie; Liu, Wei; Spence, John C H; Bruce Doak, R; Nelson, Garrett; Fromme, Petra; Fromme, Raimund; Grotjohann, Ingo; Kupitz, Christopher; Zatsepin, Nadia A; Liu, Haiguang; Basu, Shibom; Wacker, Daniel; Han, Gye Won; Katritch, Vsevolod; Boutet, Sébastien; Messerschmidt, Marc; Williams, Garth J; Koglin, Jason E; Marvin Seibert, M; Klinker, Markus; Gati, Cornelius; Shoeman, Robert L; Barty, Anton; Chapman, Henry N; Kirian, Richard A; Beyerlein, Kenneth R; Stevens, Raymond C; Li, Dianfan; Shah, Syed T A; Howe, Nicole; Caffrey, Martin; Cherezov, Vadim
2014-01-01
Lipidic cubic phase (LCP) crystallization has proven successful for high-resolution structure determination of challenging membrane proteins. Here we present a technique for extruding gel-like LCP with embedded membrane protein microcrystals, providing a continuously renewed source of material for serial femtosecond crystallography. Data collected from sub-10-μm-sized crystals produced with less than 0.5 mg of purified protein yield structural insights regarding cyclopamine binding to the Smoothened receptor.
Rotary Ultrasonic Machining of Poly-Crystalline Cubic Boron Nitride
2014-01-01
Poly-crystalline cubic boron nitride (PCBN) is one of the hardest material. Generally, so hard materials could not be machined by conventional machining methods. Therefore, for this purpose, advanced machining methods have been designed. Rotary ultrasonic machining (RUM) is included among them. RUM is based on abrasive removing mechanism of ultrasonic vibrating diamond particles, which are bonded on active part of rotating tool. It is suitable especially for machining hard and brittle materia...
Cubic to tetragonal phase transition of Tm3+ doped nanocrystals in oxyfluoride glass ceramics
Directory of Open Access Journals (Sweden)
Yiming Li
2016-02-01
Full Text Available Tm3+ ions doped β-PbF2 nanocrystals in oxyfluoride glass ceramics with different doping concentrations and thermal temperatures are prepared by a traditional melt-quenching and thermal treatment method to investigate the structure and the phase transition of Tm3+ doped nanocrystals. The structures are characterized by X-ray diffraction Rietveld analysis and confirmed with numerical simulation. The phase transitions are proved further by the emission spectra. Both of the doping concentration and thermal temperature can induce an Oh to D4h site symmetry distortion and a cubic to tetragonal phase transition. The luminescence of Tm3+ doped nanocrystals at 800 nm was modulated by the phase transition of the surrounding crystal field.
Cubic to tetragonal phase transition of Tm{sup 3+} doped nanocrystals in oxyfluoride glass ceramics
Energy Technology Data Exchange (ETDEWEB)
Li, Yiming; Fu, Yuting; Shi, Yahui; Zhang, Xiaoyu; Yu, Hua, E-mail: zhaolj@nankai.edu.cn, E-mail: yuhua@nankai.edu.cn [The Key Laboratory of Weak-Light Nonlinear Photonics, Ministry of Education, School of Physics, Nankai University, Tianjin 300071 (China); Zhao, Lijuan, E-mail: zhaolj@nankai.edu.cn, E-mail: yuhua@nankai.edu.cn [The Key Laboratory of Weak-Light Nonlinear Photonics, Ministry of Education, School of Physics, Nankai University, Tianjin 300071 (China); Applied Physics School of TEDA, Nankai University, Tianjin 300457 (China)
2016-02-15
Tm{sup 3+} ions doped β-PbF{sub 2} nanocrystals in oxyfluoride glass ceramics with different doping concentrations and thermal temperatures are prepared by a traditional melt-quenching and thermal treatment method to investigate the structure and the phase transition of Tm{sup 3+} doped nanocrystals. The structures are characterized by X-ray diffraction Rietveld analysis and confirmed with numerical simulation. The phase transitions are proved further by the emission spectra. Both of the doping concentration and thermal temperature can induce an O{sub h} to D{sub 4h} site symmetry distortion and a cubic to tetragonal phase transition. The luminescence of Tm{sup 3+} doped nanocrystals at 800 nm was modulated by the phase transition of the surrounding crystal field.
The traveling salesman problem on cubic and subcubic graphs
Boyd, Sylvia; van der Ster, Suzanne; Stougie, Leen
2011-01-01
We study the Travelling Salesman Problem (TSP) on the metric completion of cubic and subcubic graphs, which is known to be NP-hard. The problem is of interest because of its relation to the famous 4/3 conjecture for metric TSP, which says that the integrality gap, i.e., the worst case ratio between the optimal values of the TSP and its linear programming relaxation (the subtour elimination relaxation), is 4/3. We present the first algorithm for cubic graphs with approximation ratio 4/3. The proof uses polyhedral techniques in a surprising way, which is of independent interest. In fact we prove constructively that for any cubic graph on $n$ vertices a tour of length 4n/3-2 exists, which also implies the 4/3 conjecture, as an upper bound, for this class of graph-TSP. Recently, M\\"omke and Svensson presented a randomized algorithm that gives a 1.461-approximation for graph-TSP on general graphs and as a side result a 4/3-approximation algorithm for this problem on subcubic graphs, also settling the 4/3 conjectur...
Field-effect transistors based on cubic indium nitride.
Oseki, Masaaki; Okubo, Kana; Kobayashi, Atsushi; Ohta, Jitsuo; Fujioka, Hiroshi
2014-02-04
Although the demand for high-speed telecommunications has increased in recent years, the performance of transistors fabricated with traditional semiconductors such as silicon, gallium arsenide, and gallium nitride have reached their physical performance limits. Therefore, new materials with high carrier velocities should be sought for the fabrication of next-generation, ultra-high-speed transistors. Indium nitride (InN) has attracted much attention for this purpose because of its high electron drift velocity under a high electric field. Thick InN films have been applied to the fabrication of field-effect transistors (FETs), but the performance of the thick InN transistors was discouraging, with no clear linear-saturation output characteristics and poor on/off current ratios. Here, we report the epitaxial deposition of ultrathin cubic InN on insulating oxide yttria-stabilized zirconia substrates and the first demonstration of ultrathin-InN-based FETs. The devices exhibit high on/off ratios and low off-current densities because of the high quality top and bottom interfaces between the ultrathin cubic InN and oxide insulators. This first demonstration of FETs using a ultrathin cubic indium nitride semiconductor will thus pave the way for the development of next-generation high-speed electronics.
Malmir, Hessam; Sahimi, Muhammad; Tabar, M Reza Rahimi
2016-12-01
Packing of cubic particles arises in a variety of problems, ranging from biological materials to colloids and the fabrication of new types of porous materials with controlled morphology. The properties of such packings may also be relevant to problems involving suspensions of cubic zeolites, precipitation of salt crystals during CO_{2} sequestration in rock, and intrusion of fresh water in aquifers by saline water. Not much is known, however, about the structure and statistical descriptors of such packings. We present a detailed simulation and microstructural characterization of packings of nonoverlapping monodisperse cubic particles, following up on our preliminary results [H. Malmir et al., Sci. Rep. 6, 35024 (2016)2045-232210.1038/srep35024]. A modification of the random sequential addition (RSA) algorithm has been developed to generate such packings, and a variety of microstructural descriptors, including the radial distribution function, the face-normal correlation function, two-point probability and cluster functions, the lineal-path function, the pore-size distribution function, and surface-surface and surface-void correlation functions, have been computed, along with the specific surface and mean chord length of the packings. The results indicate the existence of both spatial and orientational long-range order as the the packing density increases. The maximum packing fraction achievable with the RSA method is about 0.57, which represents the limit for a structure similar to liquid crystals.
Dry Powder Precursors of Cubic Liquid Crystalline Nanoparticles (cubosomes)
Spicer, Patrick T.; Small, William B.; Small, William B.; Lynch, Matthew L.; Burns, Janet L.
2002-08-01
Cubosomes are dispersed nanostructured particles of cubic phase liquid crystal that have stimulated significant research interest because of their potential for application in controlled-release and drug delivery. Despite the interest, cubosomes can be difficult to fabricate and stabilize with current methods. Most of the current work is limited to liquid phase processes involving high shear dispersion of bulk cubic liquid crystalline material into sub-micron particles, limiting application flexibility. In this work, two types of dry powder cubosome precursors are produced by spray-drying: (1) starch-encapsulated monoolein is produced by spray-drying a dispersion of cubic liquid crystalline particles in an aqueous starch solution and (2) dextran-encapsulated monoolein is produced by spray-drying an emulsion formed by the ethanol-dextran-monoolein-water system. The encapsulants are used to decrease powder cohesion during drying and to act as a soluble colloidal stabilizer upon hydration of the powders. Both powders are shown to form (on average) 0.6 μm colloidally-stable cubosomes upon addition to water. However, the starch powders have a broader particle size distribution than the dextran powders because of the relative ease of spraying emulsions versus dispersions. The developed processes enable the production of nanostructured cubosomes by end-users rather than just specialized researchers and allow tailoring of the surface state of the cubosomes for broader application.
Malmir, Hessam; Sahimi, Muhammad; Tabar, M. Reza Rahimi
2016-12-01
Packing of cubic particles arises in a variety of problems, ranging from biological materials to colloids and the fabrication of new types of porous materials with controlled morphology. The properties of such packings may also be relevant to problems involving suspensions of cubic zeolites, precipitation of salt crystals during CO2 sequestration in rock, and intrusion of fresh water in aquifers by saline water. Not much is known, however, about the structure and statistical descriptors of such packings. We present a detailed simulation and microstructural characterization of packings of nonoverlapping monodisperse cubic particles, following up on our preliminary results [H. Malmir et al., Sci. Rep. 6, 35024 (2016), 10.1038/srep35024]. A modification of the random sequential addition (RSA) algorithm has been developed to generate such packings, and a variety of microstructural descriptors, including the radial distribution function, the face-normal correlation function, two-point probability and cluster functions, the lineal-path function, the pore-size distribution function, and surface-surface and surface-void correlation functions, have been computed, along with the specific surface and mean chord length of the packings. The results indicate the existence of both spatial and orientational long-range order as the the packing density increases. The maximum packing fraction achievable with the RSA method is about 0.57, which represents the limit for a structure similar to liquid crystals.
Integer roots of quadratic and cubic polynomials with integer coefficients
Zelator, Konstantine
2011-01-01
The subject matter of this work is quadratic and cubic polynomial functions with integer coefficients;and all of whose roots are integers. The material of this work is directed primarily at educators,students,and teachers of mathematics,grades K12 to K20.The results of this work are expressed in Theorems3,4,and5. Of these theorems, Theorem3, is the one that most likely, the general reader of this article will have some familiarity with.In Theorem3, precise coefficient conditions are given;in order that a quadratic trinomial(with integer) have two integer roots or zeros.On the other hand, Theorems4 and5 are largely unfamiliar territory. In Theorem4, precise coefficient conditions are stated; for a monic cubic polynomial to have a double(i.e.of multiplicity 2) integer root, and a single integer root(i.e.of multiplicity 1).The entire family of such cubics can be described in terms of four groups or subfamilies; each such group being a two-integer parameter subfamily. In Theorem5, a one-integer parameter family o...
Arithmetic Problems in Cubic and Quartic Function Fields
Bembom, Tobias
2010-01-01
One of the main themes in this thesis is the description of the signature of both the infinite place and the finite places in cubic function fields of any characteristic and quartic function fields of characteristic at least 5. For these purposes, we provide a new theory which can be applied to cubic and quartic function fields and to even higher dimensional function fields. One of the striking advantages of this theory to other existing methods is that is does not use the concept of p-adic completions and we can dispense of Cardano's formulae. Another key result comprises the construction of cubic function fields of unit rank 1 and 2, with an obvious fundamental system. One of the main ingredients for such constructions is the definition of the maximum value. This definition is new and very prolific in the context of finding fundamental systems. We conclude the thesis with miscellaneous results on the divisor class number h, including a new approach for finding divisors of h.
Dynamic properties of the cubic nonlinear Schr(o)dinger equation by symplectic method
Institute of Scientific and Technical Information of China (English)
Liu Xue-Shen; Wei Jia-Yu; Ding Pei-Zhu
2005-01-01
The dynamic properties of a cubic nonlinear Schrodinger equation are investigated numerically by using the symplectic method with different space approximations. The behaviours of the cubic nonlinear Schrodinger equation are discussed with different cubic nonlinear parameters in the harmonically modulated initial condition. We show that the conserved quantities will be preserved for long-time computation but the system will exhibit different dynamic behaviours in space difference approximation for the strong cubic nonlinearity.
Field assisted sintering of dense Al-substituted cubic phase Li7La3Zr2O12 solid electrolytes
Zhang, Yanhua; Chen, Fei; Tu, Rong; Shen, Qiang; Zhang, Lianmeng
2014-12-01
High performance lithium ion conducting Li7La3Zr2O12 solid electrolytes are prepared for the first time by field assisted sintering technology (FAST). The effect of sintering temperature on the phase compositions, microstructure and Li ionic conductivity is systematically investigated. The results show that pure cubic phase LLZO can be obtained at a range of temperatures from 1100 to 1180 °C for no more than 10 min. For the sample sintered at 1150 °C, a maximum relative density of 99.8% with a total ionic conductivity as high as 5.7 × 10-4 S cm-1 are obtained at room temperature. This value is the highest among the present research. Compared with the traditional preparation methods, the current FAST is very promising to obtain high performance LLZO for its advantages of very short sintering time, a single preparation step of reaction-densification processing, and relatively lower sintering temperature.
An, Yuguo; Boterman, Romke; Atzema, Eisso; Abspoel, Michael; Scholting, Marc
2016-07-01
Robust design optimization techniques have been developed in recent years within the automotive industry with the aim of reducing scrap rates and improving process stability in sheet metal forming. These new techniques are able to take process variations and other sources of material scatter into account. Among the many material variables and inputs used, the yield criterion is an important aspect and this is used to describe the plastic behavior of sheet metals. To achieve a reliable output in an optimization study, the yield criterion selected must be representative of material response and scatter. However, simple material models that deviate from real material behavior are often used due to a lack of material data, which is usually a requirement when using more complex models. In the present research, a polycrystal plasticity-based CTFP model has been evaluated in stretch forming for a collection of highly formable sheet steel materials. The results demonstrate that the CTFP model can capture the yielding character and also detect the minor deviations presented by different coils. The stretching factor derived from the CTFP model, as opposed to the work hardening and ductility, has a dominant effect on failure for a collection of materials with similar mechanical properties. Results also indicate that plastic deformation causes texture evolution and, consequently, an evolving yield locus. Such changes in the yield locus during deformation have an effect on stretching and friction calibration in FE simulations.
Silveira, L G D; Dias, G S; Cótica, L F; Eiras, J A; Garcia, D; Sampaio, J A; Yokaichiya, F; Santos, I A
2013-11-27
Temperature-dependent and frequency-dependent dielectric investigations have been performed in TbMnO3 polycrystals sintered in either oxidative or reductive atmospheres. The results revealed the occurrence of two dielectric anomalies above 100 K, which are caused by the thermal activation of charge carriers and their motion in grain cores and grain boundaries. The temperature dependence of the bulk dc conductivity was also analysed and indicates that charge carriers move between inequivalent sites according to a variable-range-hopping mechanism. Also, a strong correlation between dielectric properties and crystalline structure was observed. Furthermore, a low-temperature dielectric relaxation, commonly reported in rare-earth manganite crystals, was observed in both samples. This relaxation follows the empirical Cole-Cole model and was attributed to small-polaron tunnelling. Polaron motion was observed to be affected by the magnetic transitions, structural properties and intrinsic anisotropies in TbMnO3. It is also worth mentioning that the dielectric anomaly due to motion of charge carriers in grain boundaries is the only one of extrinsic origin, while the anomalies related to carrier motion in grain cores and small-polaron tunnelling are intrinsic to TbMnO3.
Energy Technology Data Exchange (ETDEWEB)
Palacios G, J., E-mail: jpalacios@ipn.mx [IPN, Escuela Superior de Fisica y Matematicas, San Pedro Zacatenco 07738, Ciudad de Mexico (Mexico)
2016-11-01
The integrated intensity of Debye-Scherrer (D-S) rings, arising from an eventual second diffraction process of a diffracted X-ray beam, was calculated. This represents the amount of intensity not arriving at the detector as oriented to register the first diffraction process, and as result, a measure of secondary extinction. Thus the objective is to investigate in this way if secondary extinction affects measurements of X-ray diffraction from textured polycrystals. This has been suggested by differences of pole density maxima observed between measured first and second order pole figures in strongly textured materials. Calculations are performed for a detector scan (varying only 2θ), and the integrated intensity is determined for first and second order diffraction conditions of a general plane (hkl). Normalization through corresponding powder is performed. It is found that this special case of multiple scattering effect, indeed affects both orders essentially in the same way. If corresponding detector scan measurements verify this, then the observed differences between pole density maxima of pole figures of different order cannot be attributed to secondary extinction. Instead, they can be attributed to heterogeneous texture or error propagation. On the other hand, if the detector scans do exhibit a difference as that of pole density maxima, these differences can possibly be attributed to primary extinction. (Author)
AC Electroluminescent Processes in Pr3+-Activated (Ba0.4Ca0.6TiO3 Diphase Polycrystals
Directory of Open Access Journals (Sweden)
Nan Gao
2017-05-01
Full Text Available We investigated the properties of alternating current (AC-driven electroluminescence from (Ba0.4Ca0.6TiO3:Pr3+ diphase polycrystal-based device. The results of crystal phases and micrographs, and the symmetrical dual emissions in one AC cycle, indicate the spontaneous formation of a dielectric/phosphor/dielectric sandwich microstructure in (Ba0.4Ca0.6TiO3:Pr3+. The electroluminescent device emits a red light of 617 nm, which is attributed to the 1D2-3H4 transition of Pr3+ in the phosphor phase. At a fixed AC frequency, the intensity of electroluminescence exhibits a steep enhancement when applying an increased driving electric field that is beyond a threshold. In a fixed driving electric field, the intensity of electroluminescence shows a rapid rise at low frequencies, but reaches saturation at high frequencies. Based on a double-injection model, we discussed systematically the electroluminescent processes in a whole cycle of AC electric field, which matched well with the experimental data. Our investigation is expected to expand our understanding of such a diphase electroluminescent device, thereby promoting their applications in lighting and displays.
Kusada, Kohei; Kobayashi, Hirokazu; Yamamoto, Tomokazu; Matsumura, Syo; Sumi, Naoya; Sato, Katsutoshi; Nagaoka, Katsutoshi; Kubota, Yoshiki; Kitagawa, Hiroshi
2013-04-17
We report the first discovery of pure face-centered-cubic (fcc) Ru nanoparticles. Although the fcc structure does not exist in the bulk Ru phase diagram, fcc Ru was obtained at room temperature because of the nanosize effect. We succeeded in separately synthesizing uniformly sized nanoparticles of both fcc and hcp Ru having diameters of 2-5.5 nm by simple chemical reduction methods with different metal precursors. The prepared fcc and hcp nanoparticles were both supported on γ-Al2O3, and their catalytic activities in CO oxidation were investigated and found to depend on their structure and size.
Chang, Hankwon; Lenggoro, I. Wuled; Okuyama, Kikuo; Kim, Tae-Oh
2004-06-01
Continuous single-step fabrication of cubic nanocrystalline Y2O3:Eu3+ phosphor particles using flame spray pyrolysis was successfully conducted without any post-heat treatments. The morphology of the as-prepared particles was spherical and nonaggregated. The mean size of as-prepared particles was easily controlled by adjusting the precursor concentration. On varying the overall concentration of the precursor solution from 0.01 to 0.5 M, the crystallite size and geometric mean particle diameter varied from 38.4 nm to 50.6 nm and 263 nm to 741 nm, respectively. XRD spectra of as-prepared particles indicated that all products, regardless of the precursor concentration, showed the cubic phase with high crystallinity without any post-treatments, although residence times in the flame were very short. Upon excitation with 254 nm light, all of the as-prepared particles showed bright red emission due to the 4f-4f transitions of Eu3+ ions, and the highest photoluminescent intensity at 611 nm was found at a Eu3+ content of about 12 mol%. These results indicate the possibility of the fabrication of cubic nanocrystalline Y2O3:Eu3+ phosphors with a high production rate and high purity.
Vacancy-induced mechanical stabilization of cubic tungsten nitride
Balasubramanian, Karthik; Khare, Sanjay; Gall, Daniel
2016-11-01
First-principles methods are employed to determine the structural, mechanical, and thermodynamic reasons for the experimentally reported cubic WN phase. The defect-free rocksalt phase is both mechanically and thermodynamically unstable, with a negative single crystal shear modulus C44=-86 GPa and a positive enthalpy of formation per formula unit Hf=0.623 eV with respect to molecular nitrogen and metallic W. In contrast, WN in the NbO phase is stable, with C44=175 GPa and Hf=-0.839 eV . A charge distribution analysis reveals that the application of shear strain along [100] in rocksalt WN results in an increased overlap of the t2 g orbitals which causes electron migration from the expanded to the shortened W-W bond axes, yielding a negative shear modulus due to an energy reduction associated with new bonding states 8.1-8.7 eV below the Fermi level. A corresponding shear strain in WN in the NbO phase results in an energy increase and a positive shear modulus. The mechanical stability transition from the NaCl to the NbO phase is explored using supercell calculations of the NaCl structure containing Cv=0 %-25 % cation and anion vacancies, while keeping the N-to-W ratio constant at unity. The structure is mechanically unstable for Cvconcentration, the isotropic elastic modulus E of cubic WN is zero, but increases steeply to E =445 GPa for Cv=10 % , and then less steeply to E =561 GPa for Cv=25 % . Correspondingly, the hardness estimated using Tian's model increases from 0 to 15 to 26 GPa as Cv increases from 5% to 10% to 25%, indicating that a relatively small vacancy concentration stabilizes the cubic WN phase and that the large variations in reported mechanical properties of WN can be attributed to relatively small changes in Cv.
Cubic Phases, Cubosomes and Ethosomes for Cutaneous Application.
Esposito, Elisabetta; Drechsler, Markus; Nastruzzi, Claudio; Cortesi, Rita
2016-01-01
Cutaneous administration represents a good strategy to treat skin diseases, avoiding side effects related to systemic administration. Apart from conventional therapy, based on the use of semi-solid formulation such as gel, ointments and creams, recently the use of specialized delivery systems based on lipid has been taken hold. This review provides an overview about the use of cubic phases, cubosomes and ethosomes, as lipid systems recently proposed to treat skin pathologies. In addition in the final part of the review cubic phases, cubosomes and ethosomes are compared to solid lipid nanoparticles and lecithin organogel with respect to their potential as delivery systems for cutaneous application. It has been reported that lipid nanosystems are able to dissolve and deliver active molecules in a controlled fashion, thereby improving their bioavailability and reducing side-effects. Particularly lipid matrixes are characterized by skin affinity and biocompatibility allowing their application on skin. Indeed, after cutaneous administration, the lipid matrix of cubic phases and cubosomes coalesces with the lipids of the stratum comeum and leads to the formation of a lipid depot from which the drug associated to the nanosystem can be released in the deeper skin strata in a controlled manner. Ethosomes are characterized by a malleable structure that promotes their interaction with skin, improving their potential as skin delivery systems with respect to liposomes. Also in the case of solid lipid nanoparticles it has been suggested a deep interaction between lipid matrix and skin strata that endorses sustained and prolonged drug release. Concerning lecithin organogel, the peculiar structure of this system, where lecithin exerts a penetration enhancer role, allows a deep interaction with skin strata, promoting the transdermal absorption of the encapsulated drugs.
Cubature Formula and Interpolation on the Cubic Domain
Institute of Scientific and Technical Information of China (English)
Huiyuan Li; Jiachang Sun; Yuan Xu
2009-01-01
Several cubature formulas on the cubic domains are derived using the dis-crete Fourier analysis associated with lattice tiling, as developed in [10]. The main results consist of a new derivation of the Gaussian type cubature for the product Cheby-shev weight functions and associated interpolation polynomials on [-1,1]2, as well as new results on [-1,1]3. In particular, compact formulas for the fundamental interpo-lation polynomials are derived, based on n3/4 + (n2) nodes of a cubature formula on [-1,1]3.
CLOSED SMOOTH SURFACE DEFINED FROM CUBIC TRIANGULAR SPLINES
Institute of Scientific and Technical Information of China (English)
Ren-zhong Feng; Ren-hong Wang
2005-01-01
In order to construct closed surfaces with continuous unit normal, we introduce a new spline space on an arbitrary closed mesh of three-sided faces. Our approach generalizes an idea of Goodman and is based on the concept of 'Geometric continuity' for piecewise polynomial parametrizations. The functions in the spline space restricted to the faces are cubic triangular polynomials. A basis of the spline space is constructed of positive functions which sum to 1. It is also shown that the space is suitable for interpolating data at the midpoints of the faces.
Exotic Universal Solutions in Cubic Superstring Field Theory
Erler, Theodore
2010-01-01
We present a class of analytic solutions of cubic superstring field theory in the universal sector on a non-BPS D-brane. Computation of the action and gauge invariant overlap reveal that the solutions carry half the tension of a non-BPS D-brane. However, the solutions do not satisfy the reality condition. In fact, they display an intriguing topological structure: We find evidence that conjugation of the solutions is equivalent to a gauge transformation that cannot be continuously deformed to the identity.
Research on the Cutting Performance of Cubic Boron Nitride Tools
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
There were only two kinds of superhard tool material at the past, i.e. diamond and cubic boron nitride (CBN). Manmade diamond and CBN are manufactured by the middle of 20th century. Various manufacturing methods and manmade superhard materials were developed later. They were widely used in different industry and science areas. Recently, a new kind of superhard tool material, C 3N 4 coating film, had been developed. American physical scientists, A. M. Liu and M. L. Cohen, designed a new kind of inorganic c...
Self-trapping transition in nonlinear cubic lattices
Naether, Uta; Guzmán-Silva, Diego; Molina, Mario I; Vicencio, Rodrigo A
2013-01-01
We explore the fundamental question about the critical nonlinearity value needed to dynamically localize energy in discrete nonlinear cubic (Kerr) lattices. We focus on the effective frequency and participation ratio of the profile to determine the transition into localization, performing several numerical simulations in one-, two-, and three-dimensional lattices. A simple criterium is developed - for the case of an initially localized excitation - defining the transition region in parameter space ("dynamical tongue") from a delocalized to a localized profile. A general analytical estimate of the critical nonlinearity value for which this transition occurs is obtained.
Cubic versus spherical magnetic nanoparticles: the role of surface anisotropy.
Salazar-Alvarez, G; Qin, J; Sepelák, V; Bergmann, I; Vasilakaki, M; Trohidou, K N; Ardisson, J D; Macedo, W A A; Mikhaylova, M; Muhammed, M; Baró, M D; Nogués, J
2008-10-08
The magnetic properties of maghemite (gamma-Fe2O3) cubic and spherical nanoparticles of similar sizes have been experimentally and theoretically studied. The blocking temperature, T(B), of the nanoparticles depends on their shape, with the spherical ones exhibiting larger T(B). Other low temperature properties such as saturation magnetization, coercivity, loop shift or spin canting are rather similar. The experimental effective anisotropy and the Monte Carlo simulations indicate that the different random surface anisotropy of the two morphologies combined with the low magnetocrystalline anisotropy of gamma-Fe2O3 is the origin of these effects.
Configuration spaces of an embedding torus and cubical spaces
Jourdan, Jean-Philippe
2006-01-01
For a smooth manifold M obtained as an embedding torus, A U Cx[-1,1], we consider the ordered configuration space F_k(M) of k distinct points in M. We show that there is a homotopical cubical resolution of F_k(M) defined from the configuration spaces of A and C. From it, we deduce a universal method for the computation of the pure braid groups of a manifold. We illustrate the method in the case of the Mobius band.
Ionic Conduction in Cubic Zirconias at Low Temperatures
Institute of Scientific and Technical Information of China (English)
Ying LI; Yunfa CHEN; Jianghong GONG
2004-01-01
The ac conductivities of Y2O3 or CaO-stabilized cubic zirconias were obtained from complex impedance measurements in the temperature range from 373 to 473 K. By analyzing the temperature-dependence of the resultant dc conductivities, it was shown that the activation energies for conduction are lower than those reported previously for the same materials at high temperatures. Comparing the activation energy data with the theoretically estimated values revealed that there may exist a certain, although very small, amount of free oxygen vacancies in the test samples at low temperatures and the conduction in the test samples is a result of the migration of these free oxygen vacancies.
Cubic to tetragonal crystal lattice reconstruction during ordering or decomposition
Energy Technology Data Exchange (ETDEWEB)
Cheong, Byung-kl [Carnegie-Mellon Univ., Pittsburgh, PA (United States). Dept. of Materials Science and Engineering
1992-09-01
This thesis studied thermodynamic stability and morphology of product phases in diffusional phase transformations involving cubic-to-tetragonal crystal lattice reconstructions. Two different kinds of diffusional transformations were examined: L1{sub 0} ordering (fcc to fct lattice change) and decomposition of off-stoichiometric B2 ordering alloys accompanying bcc to fcc Bain transformation. In the first case, Fe-45 at.% Pd alloys were studied by TEM; in the second, the Bain strain relaxation during decomposition of hyper-eutectoid Cu-9.04 wt% Be alloy was studied. CuAu and InMg were also studied.
On the {P2, P3}-Factor of Cubic Graphs
Institute of Scientific and Technical Information of China (English)
GOU Kui-xiang; SUN Liang
2005-01-01
Let G = ( V, E) be a finite simple graph and Pn denote the path of order n. A spanning subgraph F is called a {P2, P3}-factor of G if each component of F is isomorphic to P2 or P3. With the path-covering method, it is proved that any connected cubic graph with at least 5 vertices has a { P2, P3 }-factor F such that | P3 (F) |≥|P2 (F) |, where P2 (F) and P3 (F) denote the set of components of P2 and P3 in F,respectively.
Inhomogeneous atomic Bose-Fermi mixtures in cubic lattices.
Cramer, M; Eisert, J; Illuminati, F
2004-11-05
We determine the ground state properties of inhomogeneous mixtures of bosons and fermions in cubic lattices and parabolic confining potentials. For finite hopping we determine the domain boundaries between Mott-insulator plateaux and hopping-dominated regions for lattices of arbitrary dimension within mean-field and perturbation theory. The results are compared with a new numerical method that is based on a Gutzwiller variational approach for the bosons and an exact treatment for the fermions. The findings can be applied as a guideline for future experiments with trapped atomic Bose-Fermi mixtures in optical lattices.
Compressibility and thermal expansion of cubic silicon nitride
DEFF Research Database (Denmark)
Jiang, Jianzhong; Lindelov, H.; Gerward, Leif
2002-01-01
The compressibility and thermal expansion of the cubic silicon nitride (c-Si3N4) phase have been investigated by performing in situ x-ray powder-diffraction measurements using synchrotron radiation, complemented with computer simulations by means of first-principles calculations. The bulk...... compressibility of the c-Si3N4 phase originates from the average of both Si-N tetrahedral and octahedral compressibilities where the octahedral polyhedra are less compressible than the tetrahedral ones. The origin of the unit cell expansion is revealed to be due to the increase of the octahedral Si-N and N-N bond...
Theoretical and Experimental Study of Time Reversal in Cubic Crystals
Institute of Scientific and Technical Information of China (English)
陆铭慧; 张碧星; 汪承灏
2004-01-01
The self-adaptive focusing of the time reversal in anisotropic media is studied theoretically and experimentally. It is conducted for the compressional wave field in the cubic crystal silicon. The experimental result is in agreement with our theoretical analysis. The focusing gain and the displacement distributions of the time reversal field are analysed in detail. It is shown that the waves from different elements of the transducer array arrive at the original place of the source simultaneously after the time reversal operation. The waveform distortions caused by the velocity anisotropy can automatically be compensated for after the time reversal processing.
Rotary Ultrasonic Machining of Poly-Crystalline Cubic Boron Nitride
Directory of Open Access Journals (Sweden)
Kuruc Marcel
2014-12-01
Full Text Available Poly-crystalline cubic boron nitride (PCBN is one of the hardest material. Generally, so hard materials could not be machined by conventional machining methods. Therefore, for this purpose, advanced machining methods have been designed. Rotary ultrasonic machining (RUM is included among them. RUM is based on abrasive removing mechanism of ultrasonic vibrating diamond particles, which are bonded on active part of rotating tool. It is suitable especially for machining hard and brittle materials (such as glass and ceramics. This contribution investigates this advanced machining method during machining of PCBN.
Cubic Plus Association Equation of State for Flow Assurance Projects
DEFF Research Database (Denmark)
dos Santos, Leticia Cotia; Abunahman, Samir Silva; Tavares, Frederico Wanderley
2015-01-01
Thermodynamic hydrate inhibitors such as methanol, ethanol, (mono) ethylene glycol (MEG), and triethylene glycol (TEG) are widely used in the oil and gas industry. On modeling these compounds, we show here how the CPA equation of state was implemented in an in-house process simulator as an in......-built model: To validate the implementation, we show calulations for binary systems containing hydrate inhibitors and water or hydrocarbons using the Cubic Plus Association (CPA) and Soave-Redlich-Kwong (SRK) equation of states, also comparing against experimental data. For streams containing natural gas...
Tensor tomography of stresses in cubic single crystals
Directory of Open Access Journals (Sweden)
Dmitry D. Karov
2015-03-01
Full Text Available The possibility of optical tomography applying to investigation of a two-dimensional and a three-dimensional stressed state in single cubic crystals has been studied. Stresses are determined within the framework of the Maxwell piezo-optic law (linear dependence of the permittivity tensor on stresses and weak optical anisotropy. It is shown that a complete reconstruction of stresses in a sample is impossible both by translucence it in the parallel planes system and by using of the elasticity theory equations. For overcoming these difficulties, it is offered to use a method of magnetophotoelasticity.
Cubic optical elements for an accommodative intraocular lens.
Simonov, Aleksey N; Vdovin, Gleb; Rombach, Michiel C
2006-08-21
We present a new accommodative intraocular lens based on a two-element varifocal Alvarez lens. The intraocular lens consists of (1) an anterior element combining a spherical lens for refractive power with a cubic surface for the varifocal effect, and (2) a posterior element with a cubic surface only. The focal length of the IOL lens changes when the superimposed refractive elements shift in opposite directions in a plane perpendicular to the optical axis. The ciliary muscle will drive the accommodation by a natural process of contraction and relaxation. Results of ray-tracing simulations of the model eye with the two-element intraocular lens are presented for on-axis and off-axis vision. The configuration of the lens is optimized to reduce refractive errors as well as effects of misalignment. A prototype with a clear aperture of ~5.7 mm is manufactured and evaluated in air with a Shack-Hartmann wave-front sensor. It provides an accommodation range of ~4 dioptres in the eye at a ~0.75-mm lateral displacement of the optical elements. The experimentally measured on-axis optical performance of the IOL lens agrees with the theoretically predicted performance.
Nonlinear structure formation in the Cubic Galileon gravity model
Barreira, Alexandre; Hellwing, Wojciech A; Baugh, Carlton M; Pascoli, Silvia
2013-01-01
We model the linear and nonlinear growth of large scale structure in the Cubic Galileon gravity model, by running a suite of N-body cosmological simulations using the {\\tt ECOSMOG} code. Our simulations include the Vainshtein screening effect, which reconciles the Cubic Galileon model with local tests of gravity. In the linear regime, the amplitude of the matter power spectrum increases by $\\sim 25%$ with respect to the standard $\\Lambda$CDM model today. The modified expansion rate accounts for $\\sim 20%$ of this enhancement, while the fifth force is responsible for only $\\sim 5%$. This is because the effective unscreened gravitational strength deviates from standard gravity only at late times, even though it can be twice as large today. In the nonlinear regime ($k \\gtrsim 0.1 h\\rm{Mpc}^{-1}$), the fifth force leads to only a modest increase ($\\lesssim 8%$) in the clustering power on all scales due to the very efficient operation of the Vainshtein mechanism. Such a strong effect is typically not seen in other...
A family of quasi-cubic blended splines and applications
Institute of Scientific and Technical Information of China (English)
SU Ben-yue; TAN Jie-qing
2006-01-01
A class of quasi-cubic B-spline base functions by trigonometric polynomials are established which inherit properties similar to those of cubic B-spline bases. The corresponding curves with a shape parameter α, defined by the introduced base functions, include the B-spline curves and can approximate the B-spline curves from both sides. The curves can be adjusted easily by using the shape parameter α, where dpi(α,t) is linear with respect to dα for the fixed t. With the shape parameter chosen properly,the defined curves can be used to precisely represent straight line segments, parabola segments, circular arcs and some transcendental curves, and the corresponding tensor product surfaces can also represent spherical surfaces, cylindrical surfaces and some transcendental surfaces exactly. By abandoning positive property, this paper proposes a new C2 continuous blended interpolation spline based on piecewise trigonometric polynomials associated with a sequence of local parameters. Illustration showed that the curves and surfaces constructed by the blended spline can be adjusted easily and freely. The blended interpolation spline curves can be shape-preserving with proper local parameters since these local parameters can be considered to be the magnification ratio to the length of tangent vectors at the interpolating points. The idea is extended to produce blended spline surfaces.
Partially Blended Constrained Rational Cubic Trigonometric Fractal Interpolation Surfaces
Chand, A. K. B.; Tyada, K. R.
2016-08-01
Fractal interpolation is an advance technique for visualization of scientific shaped data. In this paper, we present a new family of partially blended rational cubic trigonometric fractal interpolation surfaces (RCTFISs) with a combination of blending functions and univariate rational trigonometric fractal interpolation functions (FIFs) along the grid lines of the interpolation domain. The developed FIFs use rational trigonometric functions pi,j(θ) qi,j(θ), where pi,j(θ) and qi,j(θ) are cubic trigonometric polynomials with four shape parameters. The convergence analysis of partially blended RCTFIS with the original surface data generating function is discussed. We derive sufficient data-dependent conditions on the scaling factors and shape parameters such that the fractal grid line functions lie above the grid lines of a plane Π, and consequently the proposed partially blended RCTFIS lies above the plane Π. Positivity preserving partially blended RCTFIS is a special case of the constrained partially blended RCTFIS. Numerical examples are provided to support the proposed theoretical results.
Observation of Body-Centered Cubic Gold Nanocluster.
Liu, Chao; Li, Tao; Li, Gao; Nobusada, Katsuyuki; Zeng, Chenjie; Pang, Guangsheng; Rosi, Nathaniel L; Jin, Rongchao
2015-08-17
The structure of nanoparticles plays a critical role in dictating their material properties. Gold is well known to adopt face-centered cubic (fcc) structure. Herein we report the first observation of a body-centered cubic (bcc) gold nanocluster composed of 38 gold atoms protected by 20 adamantanethiolate ligands and two sulfido atoms ([Au38S2(SR)20], where R=C10H15) as revealed by single-crystal X-ray crystallography. This bcc structure is in striking contrast with the fcc structure of bulk gold and conventional Au nanoparticles, as well as the bi-icosahedral structure of [Au38(SCH2CH2Ph)24]. The bcc nanocluster has a distinct HOMO-LUMO gap of ca. 1.5 eV, much larger than the gap (0.9 eV) of the bi-icosahedral [Au38(SCH2CH2Ph)24]. The unique structure of the bcc gold nanocluster may be promising in catalytic applications.
Four-dimensional black holes in Einsteinian cubic gravity
Bueno, Pablo; Cano, Pablo A.
2016-12-01
We construct static and spherically symmetric generalizations of the Schwarzschild- and Reissner-Nordström-(anti-)de Sitter [RN-(A)dS] black-hole solutions in four-dimensional Einsteinian cubic gravity (ECG). The solutions are characterized by a single function which satisfies a nonlinear second-order differential equation. Interestingly, we are able to compute independently the Hawking temperature T , the Wald entropy S and the Abbott-Deser mass M of the solutions analytically as functions of the horizon radius and the ECG coupling constant λ . Using these we show that the first law of black-hole mechanics is exactly satisfied. Some of the solutions have positive specific heat, which makes them thermodynamically stable, even in the uncharged and asymptotically flat case. Further, we claim that, up to cubic order in curvature, ECG is the most general four-dimensional theory of gravity which allows for nontrivial generalizations of Schwarzschild- and RN-(A)dS characterized by a single function which reduce to the usual Einstein gravity solutions when the corresponding higher-order couplings are set to zero.
Novel Cubic Magnetite Nanoparticle Synthesis Using Room Temperature Ionic Liquid
Directory of Open Access Journals (Sweden)
M. Sundrarajan
2012-01-01
Full Text Available Room Temperature Ionic liquids are relatively more useful in the synthesis of inorganic nanostructured materials because of their unique properties. To synthesize the iron oxide nanoparticle in simple precipitation method, a novel ionic liquid was used as the greener medium and stabilizing agent namely “1-n-butyl-3-methylimidazolium trifluoromethane sulfonate [BMIM][TfO]”. The crystallinity, chemical structure, morphology and magnetic properties of the synthesized magnetite nanoparticles have been characterized by using X-ray diffraction (XRD, Fourier Transform Infrared (FT-IR, Scanning electron microscopy (SEM, Atomic force microscopy(AFM, Transmission electron microscopy (TEM and Vibrating sample magnetometer (VSM studies. The XRD study is divulge that the synthesized magnetite nanoparticles have inverse spinel face centered cubic structure. The FT-IR vibration peaks show the formation of Fe3O4 nanoparticles, where the vibration peak for Fe-O is deliberately presence at 584 cm-1. The average particle size of the synthesized nanoparticles is found to be 35 nm. Homogeneously dispersed cubic shape with superstructure is found through SEM, AFM and TEM examination studies. The synthesized iron oxide nanoparticles have a high saturation magnetization value of 25 emu/g, which is very much useful for biomedical applications.
Epitaxial Cubic Ce2O3 Films via Ce-CeO2 Interfacial Reaction.
Stetsovych, Vitalii; Pagliuca, Federico; Dvořák, Filip; Duchoň, Tomáš; Vorokhta, Mykhailo; Aulická, Marie; Lachnitt, Jan; Schernich, Stefan; Matolínová, Iva; Veltruská, Kateřina; Skála, Tomáš; Mazur, Daniel; Mysliveček, Josef; Libuda, Jörg; Matolín, Vladimír
2013-03-21
Thin films of reduced ceria supported on metals are often applied as substrates in model studies of the chemical reactivity of ceria based catalysts. Of special interest are the properties of oxygen vacancies in ceria. However, thin films of ceria prepared by established methods become increasingly disordered as the concentration of vacancies increases. Here, we propose an alternative method for preparing ordered reduced ceria films based on the physical vapor deposition and interfacial reaction of Ce with CeO2 films. The method yields bulk-truncated layers of cubic c-Ce2O3. Compared to CeO2 these layers contain 25% of perfectly ordered vacancies in the surface and subsurface allowing well-defined measurements of the properties of ceria in the limit of extreme reduction. Experimentally, c-Ce2O3(111) layers are easily identified by a characteristic 4 × 4 surface reconstruction with respect to CeO2(111). In addition, c-Ce2O3 layers represent an experimental realization of a normally unstable polymorph of Ce2O3. During interfacial reaction, c-Ce2O3 nucleates on the interface between CeO2 buffer and Ce overlayer and is further stabilized most likely by the tetragonal distortion of the ceria layers on Cu. The characteristic kinetics of the metal-oxide interfacial reactions may represent a vehicle for making other metastable oxide structures experimentally available.
Key parameters governing the densification of cubic-Li7La3Zr2O12 Li+ conductors
Yi, Eongyu; Wang, Weimin; Kieffer, John; Laine, Richard M.
2017-06-01
Cubic-Li7La3Zr2O12 (LLZO) is regarded as one of the most promising solid electrolytes for the construction of inherently safe, next generation all-solid-state Li batteries. Unfortunately, sintering these materials to full density with controlled grain sizes, mechanical and electrochemical properties relies on energy and equipment intensive processes. In this work, we elucidate key parameters dictating LLZO densification by tracing the compositional and structural changes during processing calcined and ball-milled Al3+ doped LLZO powders. We find that the powders undergo ion (Li+/H+) exchange during room temperature processing, such that on heating, the protonated LLZO lattice collapses and crystallizes to its constituent oxides, leading to reaction driven densification at sizes and protonation cannot be decoupled, and actually aid densification. We conclude that using fully decomposed nanoparticle mixtures, as obtained by liquid-feed flame spray pyrolysis, provides an ideal approach to use high surface and reaction energy to drive densification, resulting in pressureless sintering of Ga3+ doped LLZO thin films (25 μm) at 1130 °C/0.3 h to ideal microstructures (95 ± 1% density, 1.2 ± 0.2 μm average grain size) normally accessible only by pressure-assisted sintering. Such films offer both high ionic conductivity (1.3 ± 0.1 mS cm-1) and record low ionic area specific resistance (2 Ω cm2).
Yamashita, Osamu; Tomiyoshi, Shoichi
2002-10-01
The cooling temperatures of rectangular parallelepiped Bi and Bi0.88Sb0.12 polycrystals of various dimensions were measured at 298 K as a function of electric current in magnetic fields up to 2.17 T, where the magnetic field was aligned along the thickness (t) direction of the sample and copper current leads were soldered to the centers of two ridges along the thickness direction on two diagonally opposite corners of a rectangle with length L and width W. With this configuration, the temperature measurements were carried out at both end surfaces with the cross section (W×t). The thermoelement was not in contact with a heat sink. The maximum cooling temperature at the cooled surface increases with increasing magnetic field, but it depends strongly on not only the aspect ratio of the sample but also its thickness. It was found that geometrically optimum shaping of a thermoelement is very important for achieving high-cooling efficiency. A thermoelement made of Bi0.88Sb0.12 with optimum dimensions of L=15 mm, W=2 mm, and t=3 mm effects the high-cooling temperature of 4.2 K in a magnetic field of 2.17 T. As a result, the cooling temperature reached 74% of the cooling temperature of 5.7 K obtained with p-type Bi2Te3 of L=12 mm and W=t=4.8 mm which has a thermoelectric figure of merit of ZT=0.87 at 298 K.
Low temperature complete combustion of dilute propane over Mn-doped ZrO2 (cubic) catalysts
Indian Academy of Sciences (India)
Vasant R Choudhary; Subhabrata Banerjee; Suryakant G Pataskar
2003-08-01
Combustion of dilute propane (0.9 mol %) over Mn-doped ZrO2 catalysts prepared using different precipitating agents (viz. TMAOH, TEAOH, TPAOH, TBAOH and NH4OH), having different Mn/Zr ratios (0.05 - 0.67) and calcined at different temperatures (500-800°C), has been thoroughly investigated at different temperatures (300-500°C) and space velocities (25,000-100,000 cm3 g-1 h-1) for controlling propane emissions from LPG-fuelled vehicles. Mn-doped ZrO2 catalyst shows high propane combustion activity, particularly when its ZrO2 is in the cubic form, when its Mn/Zr ratio is close to 0.2 and when it is prepared using TMAOH as a precipitating agent and calcined at 500-600°C. Pulse reaction of propane in the absence of free-O2 over Mn-doped ZrO2 (cubic) and Mn-impregnated ZrO2 (monoclinic) catalysts has also been investigated for studying the relative reactivity and mobility of the lattice oxygen of the two catalysts. Both reactivity and mobility of the lattice oxygen of Mn-doped ZrO2 are found to be much higher than that of Mnimpregnated ZrO2. Propane combustion over Mn-doped ZrO2 catalyst involves a redox mechanism.
Synthesis of nano-scale fast ion conducting cubic Li7La3Zr2O12
Sakamoto, Jeff; Rangasamy, Ezhiylmurugan; Kim, Hyunjoung; Kim, Yunsung; Wolfenstine, Jeff
2013-10-01
A solution-based process was investigated for synthesizing cubic Li7La3Zr2O12 (LLZO), which is known to exhibit the unprecedented combination of fast ionic conductivity, and stability in air and against Li. Sol-gel chemistry was developed to prepare solid metal-oxide networks consisting of 10 nm cross-links that formed the cubic LLZO phase at 600 ° C. Sol-gel LLZO powders were sintered into 96% dense pellets using an induction hot press that applied pressure while heating. After sintering, the average LLZO grain size was 260 nm, which is 13 times smaller compared to LLZO prepared using a solid-state technique. The total ionic conductivity was 0.4 mS cm-1 at 298 K, which is the same as solid-state synthesized LLZO. Interestingly, despite the same room temperature conductivity, the sol-gel LLZO total activation energy is 0.41 eV, which 1.6 times higher than that observed in solid-state LLZO (0.26 eV). We believe the nano-scale grain boundaries give rise to unique transport phenomena that are more sensitive to temperature when compared to the conventional solid-state LLZO.
Non-spherical micelles in an oil-in-water cubic phase
DEFF Research Database (Denmark)
Leaver, M.; Rajagopalan, V.; Ulf, O.
2000-01-01
The cubic phase formed between the microemulsion and hexagonal phases of the ternary pentaethylene glycol dodecyl ether (C12E5)-decane-water system and that doped with small amounts of sodium dodecylsulfate (SDS) have been investigated. The presence of discrete oil-swollen micelles in the cubic...... phase, both with and without SDS, was established by NMR self-diffusion. In addition H-2 NMR relaxation experiments have demonstrated that the micelles in the cubic phase are non-spherical, having grown and changed shape upon formation of the cubic phase from the micellar solution. Small angle...... scattering experiments indicate that the lattice parameter for the cubic phase is inconsistent with a simple packing of micelles. Whilst insufficient reflections were observed to establish the space group of the cubic phase uniquely, those that were are consistent with two commonly observed space groups...
A. Beléndez; ALVAREZ, M. L.; Francés, J.; S. Bleda; Beléndez, T.; Nájera, A.; Arribas, E.
2012-01-01
Accurate approximate closed-form solutions for the cubic-quintic Duffing oscillator are obtained in terms of elementary functions. To do this, we use the previous results obtained using a cubication method in which the restoring force is expanded in Chebyshev polynomials and the original nonlinear differential equation is approximated by a cubic Duffing equation. Explicit approximate solutions are then expressed as a function of the complete elliptic integral of the first kind and the Jacobi ...
Quantum-Carnot engine for particle confined to cubic potential
Sutantyo, Trengginas Eka P.; Belfaqih, Idrus H.; Prayitno, T. B.
2015-09-01
Carnot cycle consists of isothermal and adiabatic processes which are reversible. Using analogy in quantum mechanics, these processes can be well explained by replacing variables in classical process with a quantum system. Quantum system which is shown in this paper is a particle that moves under the influence of a cubic potential which is restricted only to the state of the two energy levels. At the end, the efficiency of the system is shown as a function of the width ratio between the initial conditions and the farthest wall while expanding. Furthermore, the system efficiency will be considered 1D and 2D cases. The providing efficiencies are different due to the influence of the degeneration of energy and the degrees of freedom of the system.
Gauge Fixing of Modified Cubic Open Superstring Field Theory
Kohriki, Maiko; Kunitomo, Hiroshi
2011-01-01
The gauge-fixing problem of modified cubic open superstring field theory is discussed in detail both for the Ramond and Neveu-Schwarz sectors in the Batalin-Vilkovisky (BV) framework. We prove for the first time that the same form of action as the classical gauge-invariant one with the ghost-number constraint on the string field relaxed gives the master action satisfying the BV master equation. This is achieved by identifying independent component fields based on the analysis of the kernel structure of the inverse picture changing operator. The explicit gauge-fixing conditions for the component fields are discussed. In a kind of $b_0=0$ gauge, we explicitly obtain the NS propagator which has poles at the zeros of the Virasoro operator $L_0$.
Quantum-Carnot engine for particle confined to cubic potential
Energy Technology Data Exchange (ETDEWEB)
Sutantyo, Trengginas Eka P., E-mail: trengginas.eka@gmail.com; Belfaqih, Idrus H., E-mail: idrushusin21@gmail.com; Prayitno, T. B., E-mail: teguh-budi@unj.ac.id [Department of Physics, State University of Jakarta, Jl. Pemuda No.10, Rawamangun, Jakarta Timur 13220 (Indonesia)
2015-09-30
Carnot cycle consists of isothermal and adiabatic processes which are reversible. Using analogy in quantum mechanics, these processes can be well explained by replacing variables in classical process with a quantum system. Quantum system which is shown in this paper is a particle that moves under the influence of a cubic potential which is restricted only to the state of the two energy levels. At the end, the efficiency of the system is shown as a function of the width ratio between the initial conditions and the farthest wall while expanding. Furthermore, the system efficiency will be considered 1D and 2D cases. The providing efficiencies are different due to the influence of the degeneration of energy and the degrees of freedom of the system.
Perbaikan Metode Penghitungan Debit Sungai Menggunakan Cubic Spline Interpolation
Directory of Open Access Journals (Sweden)
Budi I. Setiawan
2007-09-01
Full Text Available Makalah ini menyajikan perbaikan metode pengukuran debit sungai menggunakan fungsi cubic spline interpolation. Fungi ini digunakan untuk menggambarkan profil sungai secara kontinyu yang terbentuk atas hasil pengukuran jarak dan kedalaman sungai. Dengan metoda baru ini, luas dan perimeter sungai lebih mudah, cepat dan tepat dihitung. Demikian pula, fungsi kebalikannnya (inverse function tersedia menggunakan metode. Newton-Raphson sehingga memudahkan dalam perhitungan luas dan perimeter bila tinggi air sungai diketahui. Metode baru ini dapat langsung menghitung debit sungaimenggunakan formula Manning, dan menghasilkan kurva debit (rating curve. Dalam makalah ini dikemukaan satu canton pengukuran debit sungai Rudeng Aceh. Sungai ini mempunyai lebar sekitar 120 m dan kedalaman 7 m, dan pada saat pengukuran mempunyai debit 41 .3 m3/s, serta kurva debitnya mengikuti formula: Q= 0.1649 x H 2.884 , dimana Q debit (m3/s dan H tinggi air dari dasar sungai (m.
On the undamped vibration absorber with cubic stiffness characteristics
Gatti, G.
2016-09-01
In order to improve the performance of a vibration absorber, a nonlinear spring can be used on purpose. This paper presents an analytical insight on the characteristics of an undamped nonlinear vibration absorber when it is attached to a linear spring-mass-damper oscillator. In particular, the nonlinear attachment is modelled as a Duffing's oscillator with a spring characteristics having a linear positive stiffness term plus a cubic stiffness term. The effects of the nonlinearity, mass ratio and frequency ratio are investigated based on an approximate analytical formulation of the amplitude-frequency equation. Comparisons to the linear case are shown in terms of the frequency response curves. The nonlinear absorber seems to show an improved robustness to mistuning respect to the corresponding linear device. However, such a better robustness may be limited by some instability of the expected harmonic response.
Cubic Spline Interpolation Reveals Different Evolutionary Trends of Various Species
Directory of Open Access Journals (Sweden)
Li Zhiqiang
2016-01-01
Full Text Available Instead of being uniform in each branch of the biological evolutionary tree, the speed of evolution, measured in the number of mutations over a fixed number of years, seems to be much faster or much slower than average in some branches of the evolutionary tree. This paper describes an evolutionary trend discovery algorithm that uses cubic spline interpolation for various branches of the evolutionary tree. As shown in an example, within the vertebrate evolutionary tree, human evolution seems to be currently speeding up while the evolution of chickens is slowing down. The new algorithm can automatically identify those branches and times when something unusual has taken place, aiding data analytics of evolutionary data.
Palladium in cubic silicon carbide: Stability and kinetics
Roma, Guido
2009-12-01
Several technological applications of silicon carbide are concerned with the introduction of palladium impurities. Be it intentional or not, this may lead to the formation of silicides. Not only this process is not well understood, but the basic properties of palladium impurities in silicon carbide, such as solubility or diffusion mechanisms, are far from being known. Here the stability and kinetics of isolated Pd impurities in cubic silicon carbide are studied by first principles calculations in the framework of density functional theory. The preferential insertion sites, as well as the main migration mechanisms, are analyzed and presented here, together with the results for solution and migration energies. The early stages of nucleation are discussed based on the properties of isolated impurities and the smallest clusters.
Four-dimensional black holes in Einsteinian cubic gravity
Bueno, Pablo
2016-01-01
We construct static and spherically symmetric generalizations of the Schwarzschild- and Reissner-Nordstr\\"om-(Anti) de Sitter (RN-(A)dS) black-hole solutions in four-dimensional Einsteinian cubic gravity (ECG). The solutions are determined by a single blackening factor which satisfies a non-linear second-order differential equation. Interestingly, we are able to compute independently the Hawking temperature $T$, the Wald entropy $\\mathsf{S}$ and the Abbott-Deser mass $M$ of the solutions analytically as functions of the horizon radius and the ECG coupling constant $\\lambda$. Using these we show that the first law of black-hole mechanics is exactly satisfied. Some of the solutions have positive specific heat, which makes them thermodynamically stable, even in the uncharged and asymptotically flat case.
Structure and energetics of nanotwins in cubic boron nitrides
Zheng, Shijian; Zhang, Ruifeng; Huang, Rong; Taniguchi, Takashi; Ma, Xiuliang; Ikuhara, Yuichi; Beyerlein, Irene J.
2016-08-01
Recently, nanotwinned cubic boron nitrides (NT c-BN) have demonstrated extraordinary leaps in hardness. However, an understanding of the underlying mechanisms that enable nanotwins to give orders of magnitude increases in material hardness is still lacking. Here, using transmission electron microscopy, we report that the defect density of twin boundaries depends on nanotwin thickness, becoming defect-free, and hence more stable, as it decreases below 5 nm. Using ab initio density functional theory calculations, we reveal that the Shockley partials, which may dominate plastic deformation in c-BNs, show a high energetic barrier. We also report that the c-BN twin boundary has an asymmetrically charged electronic structure that would resist migration of the twin boundary under stress. These results provide important insight into possible nanotwin hardening mechanisms in c-BN, as well as how to design these nanostructured materials to reach their full potential in hardness and strength.
Linear and cubic dynamic susceptibilities in quantum spin glass
Busiello, G; Sushkova, V G
2001-01-01
The low temperature behaviour of the dynamic nonlinear (cubic) susceptibility chi sub 3 sup ' (omega, T) in quantum d-dimensional Ising spin glass with short-range interactions between spins is investigated in terms of the quantum droplet model and the quantum-mechanical nonlinear response theory is employed. We have revealed a glassy like behaviour of droplet dynamics. The frequency dependence of chi sub 3 sup ' (omega, T) is very remarkable, the temperature dependence is found at very low temperatures (quantum regime). The nonlinear response depends on the tunneling rate for a droplet which regulates the strength of quantum fluctuations. This response has a strong dependence on the distribution of droplet free energies and on the droplet length scale average. Implications for experiments in quantum spin glasses like disordered dipolar quantum Ising magnet LiHo sub x Y sub 1 sub - sub x F sub 4 and pseudospin are noted.
A cubic autocatalytic reaction in a continuous stirred tank reactor
Energy Technology Data Exchange (ETDEWEB)
Yakubu, Aisha Aliyu; Yatim, Yazariah Mohd [School of Mathematical Sciences, Universiti Sains Malaysia, 11800 USM, Penang Malaysia (Malaysia)
2015-10-22
In the present study, the dynamics of the cubic autocatalytic reaction model in a continuous stirred tank reactor with linear autocatalyst decay is studied. This model describes the behavior of two chemicals (reactant and autocatalyst) flowing into the tank reactor. The behavior of the model is studied analytically and numerically. The steady state solutions are obtained for two cases, i.e. with the presence of an autocatalyst and its absence in the inflow. In the case with an autocatalyst, the model has a stable steady state. While in the case without an autocatalyst, the model exhibits three steady states, where one of the steady state is stable, the second is a saddle point while the last is spiral node. The last steady state losses stability through Hopf bifurcation and the location is determined. The physical interpretations of the results are also presented.
Submicron cubic boron nitride as hard as diamond
Energy Technology Data Exchange (ETDEWEB)
Liu, Guoduan; Kou, Zili, E-mail: kouzili@scu.edu.cn, E-mail: yanxz@hpstar.ac.cn; Lei, Li; Peng, Fang; Wang, Qiming; Wang, Kaixue; Wang, Pei; Li, Liang; Li, Yong; Wang, Yonghua [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Yan, Xiaozhi, E-mail: kouzili@scu.edu.cn, E-mail: yanxz@hpstar.ac.cn; Li, Wentao [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203 (China); Bi, Yan [Institute of Fluid Physics and National Key Laboratory of Shockwave and Detonation Physic, China Academy of Engineering Physics, Mianyang 621900 (China); Leng, Yang [Department of Mechanical Engineering, Hong Kong University of Science and Technology, Kowloon, Hong Kong (China); He, Duanwei [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Institute of Fluid Physics and National Key Laboratory of Shockwave and Detonation Physic, China Academy of Engineering Physics, Mianyang 621900 (China)
2015-03-23
Here, we report the sintering of aggregated submicron cubic boron nitride (sm-cBN) at a pressure of 8 GPa. The sintered cBN compacts exhibit hardness values comparable to that of single crystal diamond, fracture toughness about 5-fold that of cBN single crystal, in combination with a high oxidization temperature. Thus, another way has been demonstrated to improve the mechanical properties of cBN besides reducing the grain size to nano scale. In contrast to other ultrahard compacts with similar hardness, the sm-cBN aggregates are better placed for potential industrial application, as their relative low pressure manufacturing perhaps be easier and cheaper.
PT-Symmetric Cubic Anharmonic Oscillator as a Physical Model
Mostafazadeh, A
2004-01-01
We perform a perturbative calculation of the physical observables, in particular pseudo-Hermitian position and momentum operators, the equivalent Hermitian Hamiltonian operator, and the classical Hamiltonian for the PT-symmetric cubic anharmonic oscillator, $ H=p^1/(2m)+\\mu^2x^2/2+i\\epsilon x^3 $. Ignoring terms of order $ \\epsilon^4 $ and higher, we show that this system describes an ordinary quartic anharmonic oscillator with a position-dependent mass and real and positive coupling constants. This observation elucidates the classical origin of the reality and positivity of the energy spectrum. We also discuss the quantum-classical correspondence for this PT-symmetric system, compute the associated conserved probability density, and comment on the issue of factor-ordering in the pseudo-Hermitian canonical quantization of the underlying classical system.
Enhanced initial protein adsorption on an engineered nanostructured cubic zirconia
Sabirianov, R F; Namavar, F
2010-01-01
Motivated by experimentally observed biocompatibility enhancement of nanoengineered cubic zirconia ZrO2 coatings to mesenchymal stromal cells, we have carried out computational analysis of the initial immobilization of one of known structural fragment of the adhesive protein (fibronectin) on the corresponding surface. We constructed an atomistic model of the zirconia nano-hillock of 3-fold symmetry based on AFM and TEM images. First-principle quantum-mechanical calculations show a substantial variation of electrostatic potential at the hillock due to the presence of surface features such as edges and vertexes. Using an implemented Monte Carlo simulated annealing method we found the orientation of the immobilized protein on the zirconia surface (both flat and nanostructured) and contribution of the each amino acid residue from the protein sequence to the adsorption energy. Accounting for the variation of the dielectric permittivity at the protein-implant interface we use a model distance-dependent dielectric f...
Inverse cubic law of index fluctuation distribution in Indian markets
Pan, R K; Pan, Raj Kumar; Sinha, Sitabhra
2006-01-01
One of the principal statistical features characterizing the activity in financial markets is the distribution of fluctuations in market indicators such as the index. While the developed stock markets such as the New York Stock Exchange (NYSE) have been found to show heavy-tailed fluctuation distribution, there have been claims that emerging markets behave differently. Here we investigate the distribution of several indices from the Indian financial market, one of the largest emerging markets in the world. We have used both tick-by-tick data from the National Stock Exchange (NSE) and daily closing data from both NSE and Bombay Stock Exchange (BSE). We find that the cumulative distribution of index fluctuations has long tails consistent with a power law having exponent $\\alpha \\approx 3$, independent of the time-scale of observation or the market index used for the analysis. This ``inverse cubic law'' is quantitatively similar to what has been observed in developed markets, thereby providing strong evidence th...
Entanglement across a cubic interface in 3+1 dimensions
Devakul, Trithep; Singh, Rajiv R. P.
2014-08-01
We calculate the area, edge, and corner Renyi entanglement entropies in the ground state of the transverse-field Ising model, on a simple-cubic lattice, by high-field and low-field series expansions. We find that while the area term is positive and the line term is negative as required by strong subadditivity, the corner contributions are positive in three dimensions. Analysis of the series suggests that the expansions converge up to the physical critical point from both sides. The leading area-law Renyi entropies match nicely from the high- and low-field expansions at the critical point, forming a sharp cusp there. We calculate the coefficients of the logarithmic divergence associated with the corner entropy and compare them with conformal field theory results with smooth interfaces and find a striking correspondence.
Energy Density Bounds in Cubic Quasi-Topological Cosmology
dS, U Camara; Sotkov, G M
2013-01-01
We investigate the thermodynamical and causal consistency of cosmological models of the cubic Quasi-Topological Gravity (QTG) in four dimensions, as well as their phenomenological consequences. Specific restrictions on the maximal values of the matter densities are derived by requiring the apparent horizon's entropy to be a non-negative, non-decreasing function of time. The QTG counterpart of the Einstein-Hilbert (EH) gravity model of linear equation of state is studied in detail. An important feature of this particular QTG cosmological model is the new early-time acceleration period of the evolution of the Universe, together with the standard late-time acceleration present in the original EH model. The QTG correction to the causal diamond's volume is also calculated.
Room temperature quantum emission from cubic silicon carbide nanoparticles.
Castelletto, Stefania; Johnson, Brett C; Zachreson, Cameron; Beke, David; Balogh, István; Ohshima, Takeshi; Aharonovich, Igor; Gali, Adam
2014-08-26
The photoluminescence (PL) arising from silicon carbide nanoparticles has so far been associated with the quantum confinement effect or to radiative transitions between electronically active surface states. In this work we show that cubic phase silicon carbide nanoparticles with diameters in the range 45-500 nm can host other point defects responsible for photoinduced intrabandgap PL. We demonstrate that these nanoparticles exhibit single photon emission at room temperature with record saturation count rates of 7 × 10(6) counts/s. The realization of nonclassical emission from SiC nanoparticles extends their potential use from fluorescence biomarker beads to optically active quantum elements for next generation quantum sensing and nanophotonics. The single photon emission is related to single isolated SiC defects that give rise to states within the bandgap.
Spatial 't Hooft loop to cubic order in hot QCD
Giovannangeli, P
2002-01-01
Spatial 't Hooft loops of strength k measure the qualitative change in the behaviour of electric colour flux in confined and deconfined phase of SU (N) gauge theory. They show an area law in the deconfined phase, known analytica lly to two loop order with a ``k-scaling'' law k(N-k). In this paper we comput e the O(g^3) correction to the tension. It is due to neutral gluon fields that get their mass through interaction with the wall. The simple k-scaling is lost in cubic order. The generic problem of non-convexity shows up in this order an d the cure is provided. The result for large N is explicitely given. We show tha t nonperturbative effects appear at O(g^5).
Plasmon polaritons in cubic lattices of spherical metallic nanoparticles
Lamowski, Simon; Mariani, Eros; Weick, Guillaume; Pauly, Fabian
2016-01-01
We investigate theoretically plasmon polaritons in cubic lattices of interacting spherical metallic nanoparticles. Dipolar localized surface plasmons on each nanoparticle couple through the near field dipole-dipole interaction and form collective plasmons which extend over the whole metamaterial. Coupling these collective plasmons in turn to photons leads to plasmon polaritons. We derive within a quantum model general semi-analytical expressions to evaluate both plasmon and plasmon-polariton dispersions that fully account for nonlocal effects in the dielectric function of the metamaterial. Within this model, we discuss the influence of different lattice symmetries and predict related polaritonic gaps within the near-infrared to the visible range of the spectrum that depend on wavevector direction and polarization.
Cubic Derivative Interactions and Asymptotic Dynamics of the Galileon Vacuum
De Arcia, Roberto; León, Genly; Nucamendi, Ulises; Quiros, Israel
2015-01-01
In this paper we apply the tools of the dynamical systems theory in order to uncover the whole asymptotic structure of the vacuum interactions of a galileon model with a cubic derivative interaction term. It is shown that, contrary to what occurs in the presence of background matter, the galileon interactions of vacuum appreciably modify the late-time cosmic dynamics. In particular, a local late-time attractor representing phantom behavior arises which is inevitably associated with a big rip singularity. It seems that the gravitational interactions of the background matter with the galileon screen the effects of the gravitational self-interactions of the galileon, thus erasing any potential modification of the late-time dynamics by the galileon vacuum processes. Unlike other galileon models inspired in the DGP scenario, self-accelerating solutions do not arise in this model.
Quantum corrections for the cubic Galileon in the covariant language
Saltas, Ippocratis D.; Vitagliano, Vincenzo
2017-05-01
We present for the first time an explicit exposition of quantum corrections within the cubic Galileon theory including the effect of quantum gravity, in a background- and gauge-invariant manner, employing the field-reparametrisation approach of the covariant effective action at 1-loop. We show that the consideration of gravitational effects in combination with the non-linear derivative structure of the theory reveals new interactions at the perturbative level, which manifest themselves as higher-operators in the associated effective action, which' relevance is controlled by appropriate ratios of the cosmological vacuum and the Galileon mass scale. The significance and concept of the covariant approach in this context is discussed, while all calculations are explicitly presented.
Lipidic cubic phase serial millisecond crystallography using synchrotron radiation
Directory of Open Access Journals (Sweden)
Przemyslaw Nogly
2015-03-01
Full Text Available Lipidic cubic phases (LCPs have emerged as successful matrixes for the crystallization of membrane proteins. Moreover, the viscous LCP also provides a highly effective delivery medium for serial femtosecond crystallography (SFX at X-ray free-electron lasers (XFELs. Here, the adaptation of this technology to perform serial millisecond crystallography (SMX at more widely available synchrotron microfocus beamlines is described. Compared with conventional microcrystallography, LCP-SMX eliminates the need for difficult handling of individual crystals and allows for data collection at room temperature. The technology is demonstrated by solving a structure of the light-driven proton-pump bacteriorhodopsin (bR at a resolution of 2.4 Å. The room-temperature structure of bR is very similar to previous cryogenic structures but shows small yet distinct differences in the retinal ligand and proton-transfer pathway.
Hairy black holes in cubic quasi-topological gravity
Dykaar, Hannah; Hennigar, Robie A.; Mann, Robert B.
2017-05-01
We construct a class of five dimensional black hole solutions to cubic quasi-topological gravity with conformal scalar hair and study their thermodynamics. We find these black holes provide the second example of black hole λ-lines: a line of second order (continuous) phase transitions, akin to the fluid/superfluid transition of 4He. Examples of isolated critical points are found for spherical black holes, marking the first in the literature to date. We also find various novel and interesting phase structures, including an isolated critical point occurring in conjunction with a double reentrant phase transition. The AdS vacua of the theory are studied, finding ghost-free configurations where the scalar field takes on a non-zero constant value, in notable contrast to the five dimensional Lovelock case.
Structure and energetics of nanotwins in cubic boron nitrides
Energy Technology Data Exchange (ETDEWEB)
Zheng, Shijian, E-mail: sjzheng@imr.ac.cn, E-mail: zrf@buaa.edu.cn; Ma, Xiuliang [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Zhang, Ruifeng, E-mail: sjzheng@imr.ac.cn, E-mail: zrf@buaa.edu.cn [School of Materials Science and Engineering, and International Research Institute for Multidisciplinary Science, Beihang University, Beijing 100191 (China); Huang, Rong [Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, Shanghai 200062 (China); Taniguchi, Takashi [National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); Ikuhara, Yuichi [Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya 456-8587 (Japan); Institute of Engineering Innovation, The University of Tokyo, Tokyo 113-8656 (Japan); Beyerlein, Irene J. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
2016-08-22
Recently, nanotwinned cubic boron nitrides (NT c-BN) have demonstrated extraordinary leaps in hardness. However, an understanding of the underlying mechanisms that enable nanotwins to give orders of magnitude increases in material hardness is still lacking. Here, using transmission electron microscopy, we report that the defect density of twin boundaries depends on nanotwin thickness, becoming defect-free, and hence more stable, as it decreases below 5 nm. Using ab initio density functional theory calculations, we reveal that the Shockley partials, which may dominate plastic deformation in c-BNs, show a high energetic barrier. We also report that the c-BN twin boundary has an asymmetrically charged electronic structure that would resist migration of the twin boundary under stress. These results provide important insight into possible nanotwin hardening mechanisms in c-BN, as well as how to design these nanostructured materials to reach their full potential in hardness and strength.
THERMODYNAMIC PARAMETERS OF LEAD SULFIDE CRYSTALS IN THE CUBIC PHASE
Directory of Open Access Journals (Sweden)
T. O. Parashchuk
2016-07-01
Full Text Available Geometric and thermodynamic parameters of cubic PbS crystals were obtained using the computer calculations of the thermodynamic parameters within density functional theory method DFT. Cluster models for the calculation based on the analysis of the crystal and electronic structure. Temperature dependence of energy ΔE and enthalpy ΔH, Gibbs free energy ΔG, heat capacity at constant pressure CP and constant volume CV, entropy ΔS were determined on the basis of ab initio calculations of the crystal structure of molecular clusters. Analytical expressions of temperature dependences of thermodynamic parameters which were approximated with quantum-chemical calculation points have been presented. Experimental results compared with theoretically calculated data.
Adaptive Predistortion Using Cubic Spline Nonlinearity Based Hammerstein Modeling
Wu, Xiaofang; Shi, Jianghong
In this paper, a new Hammerstein predistorter modeling for power amplifier (PA) linearization is proposed. The key feature of the model is that the cubic splines, instead of conventional high-order polynomials, are utilized as the static nonlinearities due to the fact that the splines are able to represent hard nonlinearities accurately and circumvent the numerical instability problem simultaneously. Furthermore, according to the amplifier's AM/AM and AM/PM characteristics, real-valued cubic spline functions are utilized to compensate the nonlinear distortion of the amplifier and the following finite impulse response (FIR) filters are utilized to eliminate the memory effects of the amplifier. In addition, the identification algorithm of the Hammerstein predistorter is discussed. The predistorter is implemented on the indirect learning architecture, and the separable nonlinear least squares (SNLS) Levenberg-Marquardt algorithm is adopted for the sake that the separation method reduces the dimension of the nonlinear search space and thus greatly simplifies the identification procedure. However, the convergence performance of the iterative SNLS algorithm is sensitive to the initial estimation. Therefore an effective normalization strategy is presented to solve this problem. Simulation experiments were carried out on a single-carrier WCDMA signal. Results show that compared to the conventional polynomial predistorters, the proposed Hammerstein predistorter has a higher linearization performance when the PA is near saturation and has a comparable linearization performance when the PA is mildly nonlinear. Furthermore, the proposed predistorter is numerically more stable in all input back-off cases. The results also demonstrate the validity of the convergence scheme.
Electric quadrupole interaction in cubic BCC α-Fe
Energy Technology Data Exchange (ETDEWEB)
Błachowski, A.; Komędera, K. [Mössbauer Spectroscopy Division, Institute of Physics, Pedagogical University, ul. Podchorążych 2, PL-30-084 Kraków (Poland); Ruebenbauer, K., E-mail: sfrueben@cyf-kr.edu.pl [Mössbauer Spectroscopy Division, Institute of Physics, Pedagogical University, ul. Podchorążych 2, PL-30-084 Kraków (Poland); Cios, G.; Żukrowski, J. [AGH University of Science and Technology, Academic Center for Materials and Nanotechnology, Av. A. Mickiewicza 30, PL-30-059 Kraków (Poland); Górnicki, R. [RENON, ul. Gliniana 15/15, PL-30-732 Kraków (Poland)
2016-07-15
Mössbauer transmission spectra for the 14.41-keV resonant line in {sup 57}Fe have been collected at room temperature by using {sup 57}Co(Rh) commercial source and α-Fe strain-free single crystal as an absorber. The absorber was magnetized to saturation in the absorber plane perpendicular to the γ-ray beam axis applying small external magnetic field. Spectra were collected for various orientations of the magnetizing field, the latter lying close to the [110] crystal plane. A positive electric quadrupole coupling constant was found practically independent on the field orientation. One obtains the following value V{sub zz} = +1.61(4) × 10{sup 19} Vm{sup −2} for the (average) principal component of the electric field gradient (EFG) tensor under assumption that the EFG tensor is axially symmetric and the principal axis is aligned with the magnetic hyperfine field acting on the {sup 57}Fe nucleus. The nuclear spectroscopic electric quadrupole moment for the first excited state of the {sup 57}Fe nucleus was adopted as +0.17 b. Similar measurement was performed at room temperature using as-rolled polycrystalline α-Fe foil of high purity in the zero external field. Corresponding value for the principal component of the EFG was found as V{sub zz} = +1.92(4) × 10{sup 19} Vm{sup −2}. Hence, it seems that the origin of the EFG is primarily due to the local (atomic) electronic wave function distortion caused by the spin–orbit interaction between effective electronic spin S and incompletely quenched electronic angular momentum L. It seems as well that the lowest order term proportional to the product L·λ·S dominates, as no direction dependence of the EFG principal component is seen. The lowest order term is isotropic for a cubic symmetry as one has λ=λ 1 for cubic systems with the symbol 1 denoting unit operator and λ being the coupling parameter. - Highlights: • Precision of MS the same as MAPON • Real scans versus magnetization direction • A challenge
New cubic structure compounds as actinide host phases
Energy Technology Data Exchange (ETDEWEB)
Stefanovsky, S V [SIA Radon, 7th Rostovskii lane 2/14, Moscow 119121 (Russian Federation); Yudintsev, S V; Livshits, T S, E-mail: profstef@mtu-net.ru [Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry RAS, Staromonetny lane 35, Moscow 119017 (Russian Federation)
2010-03-15
Various compounds with fluorite (cubic zirconia) and fluorite-derived (pyrochlore, zirconolite) structures are considered as promising actinide host phases at immobilization of actinide-bearing nuclear wastes. Recently some new cubic compounds - stannate and stannate-zirconate pyrochlores, murataite and related phases, and actinide-bearing garnet structure compounds were proposed as perspective matrices for complex actinide wastes. Zirconate pyrochlore (ideally Gd{sub 2}Zr{sub 2}O{sub 7}) has excellent radiation resistance and high chemical durability but requires high temperatures (at least 1500 deg. C) to be produced by hot-pressing from sol-gel derived precursor. Partial Sn{sup 4+} substitution for Zr{sup 4+} reduces production temperature and the compounds REE{sub 2}ZrSnO{sub 7} may be hot-pressed or cold pressed and sintered at {approx}1400 deg. C. Pyrochlore, A{sub 2}B{sub 2}O{sub 7-x} (two-fold elementary fluorite unit cell), and murataite, A{sub 3}B{sub 6}C{sub 2}O{sub 20-y} (three-fold fluorite unit cell), are end-members of the polysomatic series consisting of the phases whose structures are built from alternating pyrochlore and murataite blocks (nano-sized modules) with seven- (2C/3C/2C), five- (2C/3C), eight- (3C/2C/3C) and three-fold (3C - murataite) fluorite unit cells. Actinide content in this series reduces in the row: 2C (pyrochlore) > 7C > 5C > 8C > 3C (murataite). Due to congruent melting murataite-based ceramics may be produced by melting and the firstly segregated phase at melt crystallization is that with the highest fraction of the pyrochlore modules in its structure. The melts containing up to 10 wt. % AnO{sub 2} (An = Th, U, Np, Pu) or REE/An fraction of HLW form at crystallization zoned grains composed sequentially of the 5C {yields} 8C {yields} 3C phases with the highest actinide concentration in the core and the lowest - in the rim of the grains. Radiation resistance of the 'murataite' is comparable to titanate pyrochlores. One
Extending a Property of Cubic Polynomials to Higher-Degree Polynomials
Miller, David A.; Moseley, James
2012-01-01
In this paper, the authors examine a property that holds for all cubic polynomials given two zeros. This property is discovered after reviewing a variety of ways to determine the equation of a cubic polynomial given specific conditions through algebra and calculus. At the end of the article, they will connect the property to a very famous method…
Deformation-induced structural transition in body-centred cubic molybdenum.
Wang, S J; Wang, H; Du, K; Zhang, W; Sui, M L; Mao, S X
2014-03-07
Molybdenum is a refractory metal that is stable in a body-centred cubic structure at all temperatures before melting. Plastic deformation via structural transitions has never been reported for pure molybdenum, while transformation coupled with plasticity is well known for many alloys and ceramics. Here we demonstrate a structural transformation accompanied by shear deformation from an original -oriented body-centred cubic structure to a -oriented face-centred cubic lattice, captured at crack tips during the straining of molybdenum inside a transmission electron microscope at room temperature. The face-centred cubic domains then revert into -oriented body-centred cubic domains, equivalent to a lattice rotation of 54.7°, and ~15.4% tensile strain is reached. The face-centred cubic structure appears to be a well-defined metastable state, as evidenced by scanning transmission electron microscopy and nanodiffraction, the Nishiyama-Wassermann and Kurdjumov-Sachs relationships between the face-centred cubic and body-centred cubic structures and molecular dynamics simulations. Our findings reveal a deformation mechanism for elemental metals under high-stress deformation conditions.
The Normals to a Parabola and the Real Roots of a Cubic
Bains, Majinder S.; Thoo, J. B.
2007-01-01
The geometric problem of finding the number of normals to the parabola y = x[squared] through a given point is equivalent to the algebraic problem of finding the number of distinct real roots of a cubic equation. Apollonius solved the former problem, and Cardano gave a solution to the latter. The two problems are bridged by Neil's (semi-cubical)…
Deformation-induced structural transition in body-centred cubic molybdenum
Wang, S. J.; Wang, H.; Du, K.; Zhang, W.; Sui, M. L.; Mao, S. X.
2014-03-01
Molybdenum is a refractory metal that is stable in a body-centred cubic structure at all temperatures before melting. Plastic deformation via structural transitions has never been reported for pure molybdenum, while transformation coupled with plasticity is well known for many alloys and ceramics. Here we demonstrate a structural transformation accompanied by shear deformation from an original -oriented body-centred cubic structure to a -oriented face-centred cubic lattice, captured at crack tips during the straining of molybdenum inside a transmission electron microscope at room temperature. The face-centred cubic domains then revert into -oriented body-centred cubic domains, equivalent to a lattice rotation of 54.7°, and ~15.4% tensile strain is reached. The face-centred cubic structure appears to be a well-defined metastable state, as evidenced by scanning transmission electron microscopy and nanodiffraction, the Nishiyama-Wassermann and Kurdjumov-Sachs relationships between the face-centred cubic and body-centred cubic structures and molecular dynamics simulations. Our findings reveal a deformation mechanism for elemental metals under high-stress deformation conditions.
Application and Realization of the Computer Animation Design Based on Improved Cubic B-spline Curves
Directory of Open Access Journals (Sweden)
Ni Na
2015-01-01
Full Text Available Based on the application of the cubic B-spline curves in the computer animation design, taking into account the security and confidentiality of the information, this paper improves the animation design techniques by the use of the improved cubic B-spline curves. Finally, this paper provides the relevant C language programs of the animation design.
The Normals to a Parabola and the Real Roots of a Cubic
Bains, Majinder S.; Thoo, J. B.
2007-01-01
The geometric problem of finding the number of normals to the parabola y = x[squared] through a given point is equivalent to the algebraic problem of finding the number of distinct real roots of a cubic equation. Apollonius solved the former problem, and Cardano gave a solution to the latter. The two problems are bridged by Neil's (semi-cubical)…
Cubic Invariant Spherical Surface Harmonics in Conjunction With Diffraction Strain Pole-Figures
Brakman, C.M.
1986-01-01
Four kinds of cubic invariant spherical surface harmonics are introduced. It has been shown previously that these harmonics occur in the equations relating measured diffraction (line-shift) elastic strain and macro-stresses generating these strains for the case of textured cubic materials. As a cons
Stability of the high-pressure body-centered-cubic phase of helium
Frenkel, D.
1986-01-01
This paper report absolute free-energy calculations of the fluid, body-centered-cubic, and face-centered-cubic phases of helium at T=327.04 K. We find that at and around this temperature the model potential proposed by Aziz et al. doe not yield a stable bcc phase. Quantum corrections do not alter th
Stability of the high-pressure body-centered-cubic phase of helium
Frenkel, D.
1987-01-01
This paper report absolute free-energy calculations of the fluid, body-centered-cubic, and face-centered-cubic phases of helium at T=327.04 K. We find that at and around this temperature the model potential proposed by Aziz et al. doe not yield a stable bcc phase. Quantum corrections do not alter this conclusion
Comparison of Dust Lattice Waves in Three-Dimensional Cubic Configurations
Institute of Scientific and Technical Information of China (English)
B. Farokhi; A. Hameditabar
2012-01-01
A three-dimensional (3D) dusty plasma crystalline with cubic configurations is considered. We calculate the interaction between particles up to distance √2a, implying the second-neighbor interactions for the simple cubic structure, the third-neighbor interactions for the body-centered cubic structure, and the forth-neighbor interactions the for face-centered cubic structure. Longitudinal and transverse dispersion relations are derived in arbitrary directions. The dispersion relations are studied in special directions, I.e. (1,0,0), (l,l,0)/√2, and (1,1, l)/√3- Study of dispersion relations with more neighbor interactions show that in some cases the results change physically.%A three-dimensional (3D) dusty plasma crystalline with cubic configurations is considered.We calculate the interaction between particles up to distance (√2)a,implying the second-neighbor interactions for the simple cubic structure,the third-neighbor interactions for the body-centered cubic structure,and the forth-neighbor interactions the for face-centered cubic structure.Longitudinal and transverse dispersion relations are derived in arbitrary directions.The dispersion relations are studied in special directions,i.e.(1,0,0),(1,1,0)/(√2),and (1,1,1)/(√3).Study of dispersion relations with more neighbor interactions show that in some cases the results change physically.
Extending a Property of Cubic Polynomials to Higher-Degree Polynomials
Miller, David A.; Moseley, James
2012-01-01
In this paper, the authors examine a property that holds for all cubic polynomials given two zeros. This property is discovered after reviewing a variety of ways to determine the equation of a cubic polynomial given specific conditions through algebra and calculus. At the end of the article, they will connect the property to a very famous method…
Wang, Biwei; Wang, Xinxia; Zou, Jinxiang; Yan, Yancui; Xie, Songhai; Hu, Guangzhi; Li, Yanguang; Dong, Angang
2017-03-08
Iron and nitrogen codoped carbons (Fe-N-C) have attracted increasingly greater attention as electrocatalysts for oxygen reduction reaction (ORR). Although challenging, the synthesis of Fe-N-C catalysts with highly dispersed and fully exposed active sites is of critical importance for improving the ORR activity. Here, we report a new type of graphitic Fe-N-C catalysts featuring numerous Fe single atoms anchored on a three-dimensional simple-cubic carbon framework. The Fe-N-C catalyst, derived from self-assembled Fe3O4 nanocube superlattices, was prepared by in situ ligand carbonization followed by acid etching and ammonia activation. Benefiting from its homogeneously dispersed and fully accessible active sites, highly graphitic nature, and enhanced mass transport, our Fe-N-C catalyst outperformed Pt/C and many previously reported Fe-N-C catalysts for ORR. Furthermore, when used for constructing the cathode for zinc-air batteries, our Fe-N-C catalyst exhibited current and power densities comparable to those of the state-of-the-art Pt/C catalyst.
In situ infrared spectroscopic study of cubic boron nitride thin film delamination
Institute of Scientific and Technical Information of China (English)
Yang Hang-Sheng; Zhang Jian-Ying; Nie An-Min; Zhang Xiao-Bin
2008-01-01
This paper investigates the procedure of cubic boron nitride(cBN)thin film delamination by Fourier-transform infrared(IR)spectroscopy.It finds that the apparent IR absorption peak area near 1380 cm-1 and 1073 cm-1 attributed to the B-N stretching vibration of sp2-bonded BN and the transverse optical phonon of cBN,respectively,increased up to 195% and 175% of the original peak area after film delamination induced compressive stress relaxation.The increase of IR absorption of sp2-bonded BN is found to be non-linear and hysteretic to film delamination,which suggests that the relaxation of the turbostratic BN(tBN)layer from the compressed condition is also hysteretic to film delamination.Moreover,cross-sectional transmission electron microscopic observations revealed that cBN film delamination is possible from near the aBN(amorphons BN)/tBN interface at least for films prepared by plasma-enhanced chemical vapour deposition.
Thermodynamic properties of the cubic plutonium hydride solid solution
Energy Technology Data Exchange (ETDEWEB)
Haschke, J M
1981-12-01
Pressure, temperature, and composition data for the cubic solid solution plutonium hydride phase, PuH/sub x/, have been measured by microbalance methods. Integral enthalpies and entropies of formation have been evaluated for the composition range 1.90 less than or equal to X less than or equal to 3.00. At 550/sup 0/K, ..delta..H/sup 0/ /sub f/(PuH/sub x/(s)) varies linearly from approximately (-38 +- 1) kcal mol/sup -1/ at PuH/sub 190/ to (-50 +- 1 kcal mol/sup -1/) at PuH/sub 3/ /sub 00/. Thermochemical values obtained by reevaluating tensimetric data from the literature are in excellent agreement with these results. Isotopic effects have been quantified by comparing the results for hydride and deuteride, and equations are presented for predicting ..delta..H/sup 0/ /sub f/ and ..delta..S/sup 0/ /sub f/ values for PuH/sub x/(s) and PuD/sub x/(s).
Twinning of cubic diamond explains reported nanodiamond polymorphs
Németh, Péter; Garvie, Laurence A. J.; Buseck, Peter R.
2015-12-01
The unusual physical properties and formation conditions attributed to h-, i-, m-, and n-nanodiamond polymorphs has resulted in their receiving much attention in the materials and planetary science literature. Their identification is based on diffraction features that are absent in ordinary cubic (c-) diamond (space group: Fd-3m). We show, using ultra-high-resolution transmission electron microscope (HRTEM) images of natural and synthetic nanodiamonds, that the diffraction features attributed to the reported polymorphs are consistent with c-diamond containing abundant defects. Combinations of {113} reflection and rotation twins produce HRTEM images and d-spacings that match those attributed to h-, i-, and m-diamond. The diagnostic features of n-diamond in TEM images can arise from thickness effects of c-diamonds. Our data and interpretations strongly suggest that the reported nanodiamond polymorphs are in fact twinned c-diamond. We also report a new type of twin ( rotational), which can give rise to grains with dodecagonal symmetry. Our results show that twins are widespread in diamond nanocrystals. A high density of twins could strongly influence their applications.
Oriented-cycle partitions of cubic distance-transitive graphs
Dejter, Italo J
2011-01-01
The notion of a $\\mathcal C$-ultrahomogeneous (or $\\mathcal C$-UH) graph, due to D. Isaksen et al., is adapted to digraphs and applied to the cubic distance-transitive (or CDT) graphs $G$, considered as digraphs by replacing each edge with a pair of oppositely oriented arcs, where $\\mathcal C$ is formed by oriented cycles $\\vec{C_g}$ and $(k-1)$-arcs $\\vec{P_k}$, with $g=$ girth and $k=$ largest $s$ such that $G$ is $s$-arc transitive. All CDT graphs are shown to be strongly fastened $\\{C_g\\}_{P_k}$-UH graphs, ($g=$ girth). However, only seven of them behave as $\\{\\vec{C_g}\\}_{\\vec{P}_k}$-UH digraphs. Each of these seven graphs $G$ gives place to a digraph ${\\mathcal D}(G)$ whose vertices are the $(k-1)$-arcs of $G$; an arc in ${\\mathcal D}(G)$ is traced between each two $(k-1)$-arcs in a common $g$-cycle of $G$ sharing exactly one arc, while each remaining edge of ${\\mathcal D}(G)$ is associated with a reversal of $(k-1)$-arcs in $G$. It is shown that ${\\mathcal D}(G)$ has regular indegree $=$ outdegree $=2$...
The Structure of the Cubic Coincident Site Lattice Rotation Group
Energy Technology Data Exchange (ETDEWEB)
Reed, B W; Minich, R W; Rudd, R E; Kumar, M
2004-01-13
This work is intended to be a mathematical underpinning for the field of grain boundary engineering and its relatives. The interrelationships within the set of rotations producing coincident site lattices in cubic crystals are examined in detail. Besides combining previously established but widely scattered results into a unified context, the present work details newly developed representations of the group structure in terms of strings of generators (based on quaternionic number theory, and including uniqueness proofs and rules for algebraic manipulation) as well as an easily visualized topological network model. Important results that were previously obscure or not universally understood (e.g. the {Sigma} combination rule governing triple junctions) are clarified in these frameworks. The methods also facilitate several general observations, including the very different natures of twin-limited structures in two and three dimensions, the inadequacy of the {Sigma} combination rule to determine valid quadruple nodes, and a curious link between allowable grain boundary assignments and the four-color map theorem. This kind of understanding is essential to the generation of realistic statistical models of grain boundary networks (particularly in twin-dominated systems) and is especially applicable to the field of grain boundary engineering.
Hardness analysis of cubic metal mononitrides from first principles
Fulcher, B. D.; Cui, X. Y.; Delley, B.; Stampfl, C.
2012-05-01
Density functional theory calculations are performed to evaluate the hardness of various cubic metal nitrides: rocksalt TiN, VN, ZrN, NbN, AlN, and SiN; zincblende AlN and BN; and diamond C for comparison. The isotropic elastic stiffness constants cij, bulk modulus K, shear modulus G, Young's modulus E, and isotropic Poisson's ratio ν¯ are calculated. From simulated uniaxial stress-strain curves, ideal strength values σmax in the [100], [110], and [111] directions are also evaluated for all systems. In particular, rocksalt AlN is found to possess both high elastic moduli and ideal strength. These quantities are then compared for correlations with existing experimental Vicker's hardness data. The bulk modulus is found to be a poor indicator of hardness, while E, G, 1/ν¯, and σmax all exhibit stronger correlations. With a view to circumvent the need to run computationally expensive relaxation steps, different methodologies for approximating uniaxial stress-strain curves are introduced. Utilizing the anisotropic Poisson's ratio to approximate the relaxed transverse lattice parameters at a given axial strain is a good approximation to stress-strain curves, and the ideal strengths obtained in this way exhibit strong correlations to experimental Vicker's hardness values.
Assembly of body-centered cubic crystals in hard spheres.
Xu, W-S; Sun, Z-Y; An, L-J
2011-05-01
We investigate the crystallization of monodisperse hard spheres confined by two square patterned substrates (possessing the basic character of the body-centered cubic (bcc) crystal structure) at varying substrate separations via molecular dynamics simulation. Through slowly increasing the density of the system, we find that crystallization under the influence of square patterned substrates can set in at lower densities compared with the homogeneous crystallization. As the substrate separation decreases, the density, where crystallization occurs (i.e., pressure drops), becomes small. Moreover, two distinct regimes are identified in the plane of bcc particle fraction and density for the separation range investigated. For large substrate separations, the bcc particle fraction displays a local maximum as the density is increased, and the resulting formed crystals have a polycrystalline structure. However, and more importantly, another situation emerges for small substrate separations: the capillary effects (stemming from the presence of two substrates) overwhelm the bulk driving forces (stemming from the spontaneous thermal fluctuations in the bulk) during the densification, eventually resulting in the formation of a defect-free bcc crystal (unstable with respect to the bulk hard-sphere crystals) by using two square patterned substrates.
Serial femtosecond crystallography of soluble proteins in lipidic cubic phase
Directory of Open Access Journals (Sweden)
Raimund Fromme
2015-09-01
Full Text Available Serial femtosecond crystallography (SFX at X-ray free-electron lasers (XFELs enables high-resolution protein structure determination using micrometre-sized crystals at room temperature with minimal effects from radiation damage. SFX requires a steady supply of microcrystals intersecting the XFEL beam at random orientations. An LCP–SFX method has recently been introduced in which microcrystals of membrane proteins are grown and delivered for SFX data collection inside a gel-like membrane-mimetic matrix, known as lipidic cubic phase (LCP, using a special LCP microextrusion injector. Here, it is demonstrated that LCP can also be used as a suitable carrier medium for microcrystals of soluble proteins, enabling a dramatic reduction in the amount of crystallized protein required for data collection compared with crystals delivered by liquid injectors. High-quality LCP–SFX data sets were collected for two soluble proteins, lysozyme and phycocyanin, using less than 0.1 mg of each protein.
Mechanical properties for irradiated face-centred cubic nanocrystalline metals
Xiao, X. Z.; Song, D. K.; Chu, H. J.; Xue, J. M.; Duan, H. L.
2015-01-01
In this paper, a self-consistent plasticity theory is proposed to model the mechanical behaviours of irradiated face-centred cubic nanocrystalline metals. At the grain level, a tensorial crystal model with both irradiation and grain size effects is applied for the grain interior (GI), whereas both grain boundary (GB) sliding with irradiation effect and GB diffusion are considered in modelling the behaviours of GBs. The elastic-viscoplastic self-consistent method with considering grain size distribution is developed to transit the microscopic behaviour of individual grains to the macroscopic properties of nanocrystals (NCs). The proposed theory is applied to model the mechanical properties of irradiated NC copper, and the feasibility and efficiency have been validated by comparing with experimental data. Numerical results show that: (i) irradiation-induced defects can lead to irradiation hardening in the GIs, but the hardening effect decreases with the grain size due to the increasing absorption of defects by GBs. Meanwhile, the absorbed defects would make the GBs softer than the unirradiated case. (ii) There exists a critical grain size for irradiated NC metals, which separates the grain size into the irradiation hardening dominant region (above the critical size) and irradiation softening dominant region (below the critical size). (iii) The distribution of grain size has a significant influence on the mechanical behaviours of both irradiated and unirradiated NCs. The proposed model can offer a valid theoretical foundation to study the irradiation effect on NC materials. PMID:27547091
Cubic-interaction-induced deformations of higher-spin symmetries
Joung, Euihun
2013-01-01
The deformations of higher-spin symmetries induced by cubic interactions of symmetric massless bosonic fields are analyzed within the metric-like formalism. Our analysis amends the existing classification according to gauge-algebra deformations taking into account also gauge-transformation deformations. In particular, we identify a class of couplings which leave the gauge algebra Abelian but deform one (out of three) gauge transformation, and another class of couplings which deform all three gauge transformations in (A)dS but only two in the flat-space limit. The former class is related to higher-spin algebra multiplets (representations of the global algebra) together with the massless-massive-massive couplings, which we also briefly discuss. The latter class is what makes (A)dS a distinguished background for higher-spin interactions and includes in particular the gravitational interactions of higher-spin fields, retrospectively accounting for the Fradkin-Vasiliev solution to the Aragon-Deser problem. We also...
Phase-controlled synthesis and magnetic properties of cubic and hexagonal CoO nanocrystals
Qi, Qiongqiong; Chen, Yuanzhi; Wang, Laisen; Zeng, Deqian; Peng, Dong-Liang
2016-11-01
We report facile solution approaches for the phase-controlled synthesis of rock-salt cubic CoO (c-CoO) and wurtzite-type hexagonal CoO (h-CoO) nanocrystals. In the syntheses, the cobalt precursor cobalt (II) stearate is decomposed in 1-octadecene at 320 °C, and the crystalline phase of synthesized products depend critically on the amounts of H2O. While the presence of small amounts of H2O promotes the generation of c-CoO, h-CoO is obtained in the absence of H2O. The as-prepared c-CoO nanocrystals exhibit a multi-branched morphology with several short rods growing on the direction interlaced together whereas the h-CoO nanocrystals show a multi-rod structure with several rods growing on the same base facet along the c-axis. The formation mechanisms are discussed on the basis of FTIR spectrometry data and color changes of the reaction mixture. Finally the magnetic properties of as-prepared CoO nanocrystals are measured and the results show that c-CoO nanocrystals are intrinsically antiferromagnetic with a Néel temperature of about 300 K but the antiferromagnetic ordering is not distinct for the h-CoO nanocrystals. Weak ferromagnetic contributions are also observed for both c-CoO and h-CoO nanocrystals with obvious magnetic hysteresis at 5 and 300 K. The uncompensated spins that can be induced by crystalline defects such as cation-vacancy may account for the observed weak ferromagnetism.
A method of polycrystal finite element modeling based on Voronoi diagram%一种基于Voronoi图的多晶体有限元建模方法
Institute of Scientific and Technical Information of China (English)
郑战光; 汪兆亮; 冯强; 袁帅; 王佳祥
2016-01-01
建立多晶体的细观有限元模型是研究多晶体材料局部塑性变形不均匀性的前提与基础,为了灵活地构建高可靠度的材料微结构模型,在前人研究成果的基础上提出一种基于Voronoi图并结合单元编号区域排布特点,能直接根据模型中得到的单元编号顺序依次求取单元形心坐标的构图方法就显得极为关键。该方法首先是生成特定平面或空间域里的随机点与Voronoi图基本信息,再结合单元编号区域排布特点依次直接求取中心点坐标,接着判断单元归属于距离最近的晶核所在的晶粒内,并将所得晶粒编号及单元编号以set集合形式添加到INP文件的Part部分,进而得到Voronoi多晶体有限元模型,最后以构建含10个晶粒的二维和三维多晶体模型为例和文献对比分析来进行实现与验证。结果显示：该方法可以依据单元编号区域排布特点直接得到单元编号且更加容易实现依次求取单元形心坐标,并在一定程度上降低了单元形心坐标处理的数据量和单元归属判断的难度,通过对比分析该方法建立的模型精度更接近于文献中的精确模型,它们之间的最大偏差仅为25.47 MPa,较对比文献的简化模型最小偏差还要低0.07 MPa。表明该方法可为研究人员快速构建多晶材料的Voronoi细观有限元模型提供一定的技术参考。%The mesoscopic polycrystal finite element ( PFE) model is the premise and foundation to study the local plastic deformation of polycrystalline materials. In order to construct a reliable micro-structure model of materials flexibly, a modeling method had been proposed on the basis of Voronoi diagram and regional distribution charact-eristics of units. The areal coordinates of the units could be calculated in sequence directly through the units’ num-bers by the method. Firstly, the random points and the Voronoi information in a specific plane or domain were generated. Then
Simonis, Priscilla; Vigneron, Jean Pol
2011-01-01
The cuticle of the longhorn beetle Pseudomyagrus waterhousei shows a diffuse pattern of mixed blue and violet colors. These colorations arise from a dense layer of droplet-shaped scales covering the dorsal parts of the cuticle. In spite of their lack of iridescence, these colors are shown to be structural and produced by an aggregate of internally ordered photonic-crystal grains. Computer simulations confirm that the blue and violet colors are caused by face-centered-cubic crystallites which dominantly expose their (111) surface to illumination and viewing.
Simonis, Priscilla; Vigneron, Jean Pol
2011-01-01
The cuticle of the longhorn beetle Pseudomyagrus waterhousei shows a diffuse pattern of mixed blue and violet colors. These colorations arise from a dense layer of droplet-shaped scales covering the dorsal parts of the cuticle. In spite of their lack of iridescence, these colors are shown to be structural and produced by an aggregate of internally ordered photonic-crystal grains. Computer simulations confirm that the blue and violet colors are caused by face-centered-cubic crystallites which dominantly expose their (111) surface to illumination and viewing.
Stable vortex solitons in a vectorial cubic-quintic model
Energy Technology Data Exchange (ETDEWEB)
Mihalache, D [Department of Theoretical Physics, Institute of Atomic Physics, PO Box MG-6, Bucharest (Romania); Mazilu, D [Department of Theoretical Physics, Institute of Atomic Physics, PO Box MG-6, Bucharest (Romania); Malomed, B A [Department of Interdisciplinary Studies, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978 (Israel); Lederer, F [Institute of Solid State Theory and Theoretical Optics, Friedrich-Schiller Universitaet Jena, Max-Wien-Platz 1, D-07743, Jena (Germany)
2004-05-01
We investigate the stability of vectorial (two-component) vortex solitons of two types. Their stationary shapes are identical, but their stability (which is the most important issue for spinning solitons) is drastically different. These are solitons with vorticities (S,S) and (S,-S) in the two components. The analysis is performed in a vectorial cubic-quintic model, with the two components nonlinearly coupled by the incoherent cross-phase-modulation interaction, but we expect that the results are quite generic. The stability was investigated by means of computing eigenvalues of perturbations around the stationary solitons, as well as in direct simulations. We also report new analytical results for the well-known problem of the description of the stationary form of scalar solitons in media of this type. The analytical results explain the shape of the spinning solitons, and the strong dependence of their norm (power) on the vorticity, in both the 2D and 3D cases. In this paper we also give the first estimate of the physical characteristics (power and radius) of the stable solitons with different values of S, making use of recently measured values of the necessary nonlinear parameters. All the two-component solitons of type (S,-S) are unstable. In contrast, those of type (S,S) have their stability regions, the size of which strongly depends on S. An unstable soliton always splits into a set of separating zero-spin ones, in precise compliance with the azimuthal index of the most unstable perturbation eigenmode. Direct simulations demonstrate that stable solitons readily self-trap from arbitrary initial pulses which belong to their topological class.
Energy Technology Data Exchange (ETDEWEB)
Freire, R. M. [Universidade Federal do Ceara-UFC, Grupo de Quimica de Materiais Avancados (GQMAT)- Departamento de Quimica Analitica e Fisico-Quimica (Brazil); Ribeiro, T. S.; Vasconcelos, I. F. [Universidade Federal do Ceara, Departamento de Engenharia Metalurgica e de Materiais (Brazil); Denardin, J. C. [Universidad de Santiago de Chile, USACH, Departamento de Fisica (Chile); Barros, E. B. [Universidade Federal do Ceara-UFC, Departamento de Fisica (Brazil); Mele, Giuseppe [Universita del Salento, Dipartimento di Ingegneria dell' Innovazione (Italy); Carbone, L. [IPCF-CNR, UOS Pisa (Italy); Mazzetto, S. E.; Fechine, P. B. A., E-mail: fechine@ufc.br [Universidade Federal do Ceara-UFC, Grupo de Quimica de Materiais Avancados (GQMAT)- Departamento de Quimica Analitica e Fisico-Quimica (Brazil)
2013-05-15
MZnFe{sub 2}O{sub 4} (M = Ni or Mn) cubic nanoparticles have been prepared by hydrothermal synthesis in mild conditions and short time without any procedure of calcinations. The structural and magnetic properties of the mixed ferrites were investigated by X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Moessbauer spectroscopy, vibrating sample magnetometer, and Transmission electron microscopy (TEM). X-ray analysis showed peaks characteristics of the spinel phase. The average diameter of the nanoparticles observed by TEM measurements was approximately between 4 and 10 nm. Spectroscopy study of the spinel structure was performed based on Group Theory. The predicted bands were observed in FTIR and Raman spectrum. The magnetic parameters and Moessbauer spectroscopy were measured at room temperature and superparamagnetic behavior was observed for mixed ferrites. This kind of nanoparticles can be used as precursor in drug delivery systems, magnetic hyperthermia, ferrofluids, or magnetic imaging contrast agents.
Aristov, Victor Yu; Urbanik, Grzegorz; Kummer, Kurt; Vyalikh, Denis V; Molodtsova, Olga V; Preobrajenski, Alexei B; Zakharov, Alexei A; Hess, Christian; Hänke, Torben; Büchner, Bernd; Vobornik, Ivana; Fujii, Jun; Panaccione, Giancarlo; Ossipyan, Yuri A; Knupfer, Martin
2010-03-10
The outstanding properties of graphene, a single graphite layer, render it a top candidate for substituting silicon in future electronic devices. The so far exploited synthesis approaches, however, require conditions typically achieved in specialized laboratories and result in graphene sheets whose electronic properties are often altered by interactions with substrate materials. The development of graphene-based technologies requires an economical fabrication method compatible with mass production. Here we demonstrate for the fist time the feasibility of graphene synthesis on commercially available cubic SiC/Si substrates of >300 mm in diameter, which result in graphene flakes electronically decoupled from the substrate. After optimization of the preparation procedure, the proposed synthesis method can represent a further big step toward graphene-based electronic technologies.
Polyol synthesis and characterizations of cubic ZrO{sub 2}:Eu{sup 3+} nanocrystals
Energy Technology Data Exchange (ETDEWEB)
Meetei, S. Dhiren [Department of Physics, Manipur University, Canchipur-795 003, Imphal (India); Singh, Sh. Dorendrajit, E-mail: dorendrajit@yahoo.co.in [Department of Physics, Manipur University, Canchipur-795 003, Imphal (India); Sudarsan, V. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)
2012-02-15
Highlights: Black-Right-Pointing-Pointer By polyol route nanocrystalline cubic ZrO{sub 2}:Eu{sup 3+} can be synthesized. Black-Right-Pointing-Pointer Cubic phase is the most desirable phase of zirconia. Black-Right-Pointing-Pointer Distinguishing cubic from tetragonal phase is difficult. Black-Right-Pointing-Pointer Characterizations of the samples are done by XRD, TEM, FTIR and PL. Black-Right-Pointing-Pointer Eu{sup 3+} emission peaks vary as charge transfer state in ZrO{sub 2}:Eu{sup 3+}. - Abstract: Nanocrystalline ZrO{sub 2} and ZrO{sub 2}:Eu{sup 3+} were synthesized by polyol route. The x-ray diffraction (XRD) pattern of ZrO{sub 2} shows presence of both monoclinic and tetragonal phase of zirconia, while that of ZrO{sub 2}:Eu{sup 3+} show cubic structure. Cubic phase is the most desired phase of zirconia. However, it is difficult to distinguish between the tetragonal and cubic phases solely from XRD study. Therefore, the characterizations of cubic phase in the doped samples are substantiated by transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) and photoluminescence (PL) studies. Interplaner spacing, d{sub hkl} are calculated from the selected area electron diffraction (SAED) rings and they are found to be consistent with that of cubic zirconia. FT-IR spectra of doped and undoped samples are found to be different. This is attributed to the presence of both monoclinic and tetragonal phase in the undoped sample and only cubic phase in the doped samples. PL excitation and emission spectra of the samples are studied. The asymmetry ratio is found to be less than that of the reported tetragonal phase indicating that the present analyzing samples have higher symmetry than tetragonal phase. Variations of Eu{sup 3+} emission peaks are observed as that of charge transfer state (CTS).
Leblond, Hervé; Mihalache, Dumitru; 10.1103/PHYSREVA.81.033824
2011-01-01
By using a reductive perturbation method, we derive from Maxwell-Bloch equations a cubic generalized Kadomtsev-Petviashvili equation for ultrashort spatiotemporal optical pulse propagation in cubic (Kerr-like) media without the use of the slowly varying envelope approximation. We calculate the collapse threshold for the propagation of few-cycle spatiotemporal pulses described by the generic cubic generalized Kadomtsev-Petviashvili equation by a direct numerical method and compare it to analytic results based on a rigorous virial theorem. Besides, typical evolution of the spectrum (integrated over the transverse spatial coordinate) is given and a strongly asymmetric spectral broadening of ultrashort spatiotemporal pulses during collapse is evidenced.
Mechanism of the body-centered cubic--hexagonal close-packed phase transition in iron.
Bassett, W A; Huang, E
1987-11-06
The transition from body-centered cubic to hexagonal close-packed phase in iron has been studied in a diamond anvil cell with synchrotron radiation. The hexagonal close-packed phase, when it first appears, has a ratio of lattice parameters that is significantly larger than normal. This is attributed to a displacive mechanism that causes a distortion of the hexagonal close-packed structure in a body-centered cubic matrix. The hexagonal close-packed phase adjacent to a boundary with the body-centered cubic phase is stretched in the c direction and compressed in the a direction when it first forms.
Hawkins, John A.; Rittenhouse, Jeffrey L.; Soper, Linda M.; Rittenhouse, Robert C.
2008-01-01
One of the most important crystal structures adopted by metals is characterized by the "abcabc"...stacking of close-packed layers. This structure is commonly referred to in textbooks as the cubic close-packed (ccp) or face-centered cubic (fcc) structure, since the entire lattice can be generated by replication of a face-centered cubic unit cell…
Wang, Yi; Li, Xuguang; Xue, Zhiyuan; Dai, Linsen; Xie, Songhai; Li, Quanzhi
2010-05-06
A new method has been explored to synthesize zeolite ANA crystals with regular icositetrahedron in aqueous media via transformation of zeolite Y under the conditions of low temperature, short reaction time, and without organic template. The products are perfect, almost 100% crystals. The samples prepared at different crystallization stages are measured by XRD, TEM, and SEM to investigate the transformation mechanism from zeolite Y to zeolite ANA. It has been demonstrated for the first time that the mechanism of forming a zeolite ANA polycrystal with sphere or shell morphologies is the in situ solid phase iso-structure transformation (Is-SPIST) of zeolite Y. The Is-SPIST mechanism is also supported by the results of steam-induced crystallization experiments and other assistant means, including the same Si/Al ratio, the same weight, the same particle size, and the same morphology before and after transformation of zeolite Y to zeolite ANA. It is also observed that a spherical or shell ANA polycrystal is constructed via the reconstruction from its exterior to interior, to form an ANA single crystal with a solid or hollow icositetrahedron. The main driving force of the reconstruction is considered to be the grain boundary energy existing between polycrystalline grains. This process also obeys the mechanism of in situ solid phase reconstruction (Is-SPR). Furthermore, the size and morphology of the zeolite ANA single crystal can be modified by surfactants.
Energy Technology Data Exchange (ETDEWEB)
Kaneko, Satoru; Akiyama, Kensuke; Ito, Takeshi; Yasui, Manabu; Ozawa, Takeshi; Soga, Masayasu; Motoizumi, Yu [Kanagawa Industrial Technology Center, Kanagawa Prefectural Government, 705-1 Shimo-Imaizumi, Ebina, Kanagawa 243-0435 (Japan); Yoshimoto, Mamoru, E-mail: satoru@kanagawa-iri.go.jp [Department of Innovative and Engineered Materials, Tokyo Institute of Technology, 4259 Nagatsuda, Midori-ku, Yokohama, Kanagawa 226-8503 (Japan)
2011-03-15
Epitaxial growth of MgO was verified with the relation of MgO(100) parallel to Si(100) (cubic on cubic growth) even with a large mismatch of lattice constants {approx} 22%, instead of 9% mismatch in 45{sup 0} rotation growth. MgO films prepared at higher deposition temperature showed (001) preferred orientation on Si(001) substrate. After post-annealing the MgO thin films, the pole figure of X-ray diffraction verified the epitaxial growth of cubic on cubic relation. Fe{sub 3}Si thin film was deposited on Si(001) substrate with the MgO film as buffer layer.
Directory of Open Access Journals (Sweden)
Ying Deng
2016-01-01
Full Text Available Cubic phase cobalt (Co, which can be used as a key component for composite materials given its excellent ductility and internal structure, is not easy to obtain at room temperature. In this study, oxalic acid and cobalt nitrate are used as raw materials to synthesize the cobalt oxalate precursor, which has a stable structure with a five-membered chelate ring. Cobalt oxalate microspheres, having a high internal energy content, were prepared by using mechanical solid-state reaction in the presence of a surfactant, which can produce spherical micelles. The thermal decomposition of the precursor was carried out by maintaining it in a nitrogen atmosphere at 450°C for 3 h. At the end of the procedure, 100 nm cubic phase-Co microspheres, stable at room temperature, were obtained. Isothermal and nonisothermal kinetic mechanisms of cobalt grain growth were investigated. The cubic-Co grain growth activation energy, Q, was calculated in this study to be 71.47 kJ/mol. The required reaction temperature was low, making the production process simple and suitable for industrial applications.
Study of unsteady cavitation on NACA66 hydrofoil using dynamic cubic nonlinear subgrid-scale model
Directory of Open Access Journals (Sweden)
Xianbei Huang
2015-11-01
Full Text Available In this article, we describe the use of a new dynamic cubic nonlinear model, a new nonlinear subgrid-scale model, for simulating the cavitating flow around an NACA66 series hydrofoil. For comparison, the dynamic Smagorinsky model is also used. It is found that the dynamic cubic nonlinear model can capture the turbulence spectrum, while the dynamic Smagorinsky model fails. Both models reproduce the cavity growth/destabilization cycle, but the results of the dynamic cubic nonlinear model are much smoother. The re-entrant jet is clearly captured by the models, and it is shown that the re-entrant jet cuts the cavity into two parts. In general, the dynamic cubic nonlinear model provides improvement over the dynamic Smagorinsky model for the calculation of cavitating flow.
Effects of quadratic and cubic nonlinearities on a perfectly tuned parametric amplifier
Neumeyer, S.; Sorokin, V. S.; Thomsen, J. J.
2017-01-01
We consider the performance of a parametric amplifier with perfect tuning (two-to-one ratio between the parametric and direct excitation frequencies) and quadratic and cubic nonlinearities. A forced Duffing-Mathieu equation with appended quadratic nonlinearity is considered as the model system, and approximate analytical steady-state solutions and corresponding stabilities are obtained by the method of varying amplitudes. Some general effects of pure quadratic, and mixed quadratic and cubic nonlinearities on parametric amplification are shown. In particular, the effects of mixed quadratic and cubic nonlinearities may generate additional amplitude-frequency solutions. In this case an increased response and a more phase sensitive amplitude (phase between excitation frequencies) is obtained, as compared to the case with either pure quadratic or cubic nonlinearity. Furthermore, jumps and bi-stability in the amplitude-phase characteristics are predicted, supporting previously reported experimental observations.
Rheological Properties of Cubic Liquid Crystals Formed from Monoglyceride／H2O Systems
Institute of Scientific and Technical Information of China (English)
水玲玲; 王志宁; 郑利强
2005-01-01
Monoglyceride (MO) can form various liquid crystalline phases spontaneously in the presence of various amount of water at room temperature. The appropriate compositions from binary phase diagram of MO/H2O were selected to form cubic phases. The selected systems were studied at different salt concentrations and pH value using rheological methods. There was a weak effect of salt on viscoelastic properties of cubic phases formed from MO/H2O system. Hexagonal phase was formed when pH value was decreased or increased. The viscoelasticity of cubic phases was different from that of hexagonal liquid crystals. Rheological properties of MO/H2O cubic phases were stable at pH and salt concentration similar to physiological condition.
Institute of Scientific and Technical Information of China (English)
LI She-Qiang; FU Xing-Qiu; HU Bing; DENG Jia-Jun; CHEN Lei
2009-01-01
The oxidation of formic acid on edge-truncated cubic platinum nanoparticles/C catalysts is investigated. X-ray photoelectron spectroscopy analysis indicates that the surface of edge-truncated cubic platinum nanoparticles is composed of two types of coordination sites. The oxidation behavior of formic acid on edge-truncated cubic platinum nanoparticles/C is investigated using cyclic voltammetry. The apparent activation energies are found to be 54.2, 55.0, 61.8, 69.5, 71.9, 69.26, 65.28kJ/mol at 0.15, 0.3, 0.4, 0.5, 0.6, 0.65, 0.7 V, respectively. A specific surface area activity of 1.76mA·cm~(-2) at 0.4 V indicates that the edge-truncated cubic Platinum nanoparticles are a promising anode catalyst for direct formic acid fuel cells.
Unified treatment of coupled optical and acoustic phonons in piezoelectric cubic materials
DEFF Research Database (Denmark)
Willatzen, Morten; Wang, Zhong Lin
2015-01-01
A unified treatment of coupled optical and acoustic phonons in piezoelectric cubic materials is presented whereby the lattice displacement vector and the internal ionic displacement vector are found simultaneously. It is shown that phonon couplings exist in pairs only; either between the electric...... potential and the lattice displacement coordinate perpendicular to the phonon wave vector or between the two other lattice displacement components. The former leads to coupled acousto-optical phonons by virtue of the piezoelectric effect. We then establish three new conjectures that entirely stem from...... piezoelectricity in a cubic structured material slab. First, it is shown that isolated optical phonon modes generally cannot exist in piezoelectric cubic slabs. Second, we prove that confined acousto-optical phonon modes only exist for a discrete set of in-plane wave numbers in piezoelectric cubic slabs. Third...
ON THE NUMBER OF LIMIT CYCLES OF A CUBIC SYSTEM NEAR A CUSPIDAL LOOP
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
In this paper, we investigate the limit cycle bifurcations in a cubic near-Hamiltonian system by perturbing a cuspidal loop and prove that 5 limit cycles can appear in a neighborhood of the cuspidal loop.
Russier, V.
2016-07-01
The low temperature behavior of densely packed interacting spherical single domain nanoparticles (MNP) is investigated by Monte Carlo simulations in the framework of an effective one spin model. The particles are distributed through a hard sphere like distribution with periodic boundary conditions and interact through the dipole dipole interaction (DDI) with an anisotropy energy including both cubic and uniaxial symmetry components. The cubic component is shown to play a sizable role on the value of the blocking temperature Tb only when the MNP easy axes are parallel to the cubic easy direction ([111] direction for a negative cubic anisotropy constant). The nature of the collective low temperature state, either ferromagnetic or spin glass like, is found to depend on the ratio of the anisotropy to the dipolar energies characterizing partly the disorder in the system.
Effective optical path length for tandem diffuse cubic cavities as gas absorption cell
Yu, J.; Gao, Q.; Zhang, Y. G.; Zhang, Z. G.; Wu, S. H.
2014-12-01
Tandem diffuse cubic cavities designed by connecting two single diffuse cubic-shaped cavities, A and B, with an aperture (port fraction fap) in the middle of the connecting baffle was developed as a gas absorption cell. The effective optical path length (EOPL) was evaluated by comparing the oxygen absorption signal in the cavity and in air based on tunable diode laser absorption spectroscopy (TDLAS). Experimental results manifested an enhancement of EOPL for the tandem diffuse cubic cavities as the decrease of fap and can be expressed as the sum of EOPL of two single cubic cavities at fap 0.01, which indicated that back scattering light from cavity B to cavity A cannot be ignored at this condition.
CHARACTERIZATION OF PRECIPITATES IN CUBIC SILICON CARBIDE IMPLANTED WITH 25Mg+ IONS
Energy Technology Data Exchange (ETDEWEB)
Jiang, Weilin; Spurgeon, Steven R.; Liu, Jia; Edwards, Danny J.; Schreiber, Daniel K.; Henager, Charles H.; Kurtz, Richard J.; Wang, Yongqiang
2016-09-26
The aim of this study is to characterize precipitates in Mg+ ion implanted and high-temperature annealed cubic silicon carbide using scanning transmission electron microscopy, electron energy loss spectroscopy and atom probe tomography.
Is inner core seismic anisotropy a marker of plastic flow of cubic iron?
Lincot, A; Cardin, Philippe
2015-01-01
This paper investigates whether observations of seismic anisotropy are compatible with a cubic structure of the inner core Fe alloy. We assume that anisotropy is the result of plastic deformation within a large scale flow induced by preferred growth at the inner core equator. Based on elastic moduli from the literature, bcc- or fcc-Fe produce seismic anisotropy well below seismic observations ($\\textless{}0.4\\%$). A Monte-Carlo approach allows us to generalize this result to any form of elastic anisotropy in a cubic system. Within our model, inner core global anisotropy is not compatible with a cubic structure of Fe alloy. Hence, if the inner core material is indeed cubic, large scale coherent anisotropic structures, incompatible with plastic deformation induced by large scale flow, must be present.
Structure of the body-centered cubic phase of lipid systems.
Saludjian, P; Reiss-Husson, F
1980-12-01
A new model is proposed for the structure of the body-centered cubic phase of lipid systems. Infinite rods of polar groups (and water) are arranged with axes parallel to the four cubic [unk]1 1 1[unk] directions. The hydrocarbon chains fill the space between the rods to form a continuous matrix. With this unified topology, the model explains satisfactorily the x-ray diffraction patterns of strontium soaps, lecithin, galactolipids, potassium soaps, and hexadecyltrimethylammonium bromide and explains the transition between cubic/H(II) phases. The paradoxical thermal effects on the lipid cubic phase, in particular the decrease of unit cell dimensions with increasing temperature, can be explained with the proposed model by mechanisms similar to those used for the monodimensional and bidimensional (mesomorphic) phases.
Flux pinning effect of cubic equiaxed morphology and its Ti stabilizing in Nb3Sn superconductors
Institute of Scientific and Technical Information of China (English)
ZHANG ChaoWu; ZHOU Lian; Andre SULPICE; Jean-Louis SOUBEYROUX; TANG XianDe; Christophe VERWAERDE; Gia Ky HOANG
2009-01-01
zes the cubic equiaxed phase at lower temperature so that heat reaction temperature is effectively reduced,the flux pinning performance is largely reinforced and the transport critical current density Jc is substantially promoted.
DEFF Research Database (Denmark)
Abdolvand, Hamidreza; Majkut, Marta; Oddershede, Jette
2015-01-01
) microscopy. In-situ uniaxial straining was carried out at seven steps up to 2.7% in the macroscopic direction that favors twin formation, while center-of-mass position, crystallographic orientation, elastic strain, stress, and relative volume of each grain were measured. This information was used......High anisotropy in the elastic and plastic properties of hexagonal close-packed (hcp) structured metals not only results in drastic stress variation across grain boundaries, but also heterogeneous distributions within grains. Understanding the mechanism of load sharing between different grains...... becomes more complicated when deformation twinning plays a significant role in accommodating an externally applied load. In this paper, a comprehensive study of stress development in a coarse grained strongly textured hcp polycrystal Zircaloy-2, is given using three-dimensional X-ray diffraction (3DXRD...
Xiaolong Wang; Yi Wang; Zhizhu Cao; Weizhong Zou; Liping Wang; Guojun Yu; Bo Yu; Jinjun Zhang
2013-01-01
In general, proper orthogonal decomposition (POD) method is used to deal with single-parameter problems in engineering practice, and the linear interpolation is employed to establish the reduced model. Recently, this method is extended to solve the double-parameter problems with the amplitudes being achieved by cubic B-spline interpolation. In this paper, the accuracy of reduced models, which are established with linear interpolation and cubic B-spline interpolation, respectively, is verified...
Cubic B-Spline Collocation Method for One-Dimensional Heat and Advection-Diffusion Equations
Joan Goh; Ahmad Abd. Majid; Ahmad Izani Md. Ismail
2012-01-01
Numerical solutions of one-dimensional heat and advection-diffusion equations are obtained by collocation method based on cubic B-spline. Usual finite difference scheme is used for time and space integrations. Cubic B-spline is applied as interpolation function. The stability analysis of the scheme is examined by the Von Neumann approach. The efficiency of the method is illustrated by some test problems. The numerical results are found to be in good agreement with the exact solution.
GA Based Rational cubic B-Spline Representation for Still Image Interpolation
Samreen Abbas; Malik Zawwar Hussain; Misbah Irshad
2016-01-01
In this paper, an image interpolation scheme is designed for 2D natural images. A local support rational cubic spline with control parameters, as interpolatory function, is being optimized using Genetic Algorithm (GA). GA is applied to determine the appropriate values of control parameter used in the description of rational cubic spline. Three state-of-the-art Image Quality Assessment (IQA) models with traditional one are hired for comparison with existing image interpolation schemes and perc...
High-pressure phase of the cubic spinel NiMn2O4
DEFF Research Database (Denmark)
Åsbrink, S.; Waskowska, A.; Olsen, J. Staun
1998-01-01
It has been observed that the fee spinel NiMn2O4 transforms to a tetragonal structure at about 12 GPa. The tetragonal phase does not revert to the cubic phase upon decompression and its unit-cell constants at ambient pressure are a(0)=8.65(8) and c(0)=7.88(15) Angstrom (distorted fee). Within thr......). The bulk modulus of the cubic phase is 206(4) GPa....
The double-end-pumped cubic Nd:YVO4 laser: Temperature distribution and thermal stress
Indian Academy of Sciences (India)
P Elahi; S Morshedi
2010-01-01
Thermal effects of a double-end-pumped cubic Nd:YVO4 laser crystal are investigated in this paper. A detailed analysis of temperature distribution and thermal stress in cubic crystal with circular shape pumping is discussed. It has been shown that by considering the total input powers as constant, the double-end-pumped configurations with equal pump power can be considered as having a minimum thermal effect with respect to the other end-pumped configuration.
Connected cubic s-arc-regular Cayley graphs of finite nonabelian simple groups
Institute of Scientific and Technical Information of China (English)
XU ShangJin; WU ZhengFei; DENG YunPing
2009-01-01
A graph is said to be s-arc-regular if its full automorphism group acts regularly on the set of its s-arcs. In this paper, we investigate connected cubic s-arc-regular Cayley graphs of finite nonabelian simple groups. Two sufficient and necessary conditions for such graphs to be 1- or 2-arcregular are given and based on the conditions, several infinite families of 1- or 2-arc-regular cubic Cayley graphs of alternating groups are constructed.
Exact Solutions of Discrete Complex Cubic Ginzburg-Landau Equation and Their Linear Stability
Institute of Scientific and Technical Information of China (English)
张金良; 刘治国
2011-01-01
The discrete complex cubic Ginzburg-Landau equation is an important model to describe a number of physical systems such as Taylor and frustrated vortices in hydrodynamics and semiconductor laser arrays in optics. In this paper, the exact solutions of the discrete complex cubic Ginzburg-Landau equation are derived using homogeneous balance principle and the GI/G-expansion method, and the linear stability of exact solutions is discussed.
三次系统的Berlinskii定理%ON THE BERLINSKII'S THEOREM FOR CUBIC SYSTEMS
Institute of Scientific and Technical Information of China (English)
袁蔚莉
2001-01-01
In [1]-[3], the Berlinskii's theorem of the distribution of critical points for quadratic differential systems is extended to the general n-th differential systems with n2 finite critical points. In this paper, we prove that 5- 4 distribution of critical points for cubic system is impossible by using the method of basic triangle and index formula. Then we discuss the possible distributions of cubic systems with eight, seven or six finite critical points.
Park, Yeonjoon (Inventor); Choi, Sang H. (Inventor); King, Glen C. (Inventor)
2011-01-01
Hetero-epitaxial semiconductor materials comprising cubic crystalline semiconductor alloys grown on the basal plane of trigonal and hexagonal substrates, in which misfit dislocations are reduced by approximate lattice matching of the cubic crystal structure to underlying trigonal or hexagonal substrate structure, enabling the development of alloyed semiconductor layers of greater thickness, resulting in a new class of semiconductor materials and corresponding devices, including improved hetero-bipolar and high-electron mobility transistors, and high-mobility thermoelectric devices.
Equitable and semi-equitable coloring of cubic graphs and its application in batch scheduling
Directory of Open Access Journals (Sweden)
Furmańczyk Hanna
2015-03-01
Full Text Available In the paper we consider the problems of equitable and semi-equitable coloring of vertices of cubic graphs. We show that in contrast to the equitable coloring, which is easy, the problem of semi-equitable coloring is NP-complete within a broad spectrum of graph parameters. This affects the complexity of batch scheduling of unit-length jobs with cubic incompatibility graph on three uniform processors to minimize the makespan.
Relations among Dirichlet series whose coefficients are class numbers of binary cubic forms II
Ohno, Yasuo
2011-01-01
As a continuation of the authors and Wakatsuki's previous paper [5], we study relations among Dirichlet series whose coefficients are class numbers of binary cubic forms. We show that for any integral models of the space of binary cubic forms, the associated Dirichlet series satisfies a simple explicit relation to that of the dual other than the usual functional equation. As an application, we write the functional equations of these Dirichlet series in self dual forms.
Certified Approximation of Parametric Space Curves with Cubic B-spline Curves
Shen, Liyong; Gao, Xiao-Shan
2012-01-01
Approximating complex curves with simple parametric curves is widely used in CAGD, CG, and CNC. This paper presents an algorithm to compute a certified approximation to a given parametric space curve with cubic B-spline curves. By certified, we mean that the approximation can approximate the given curve to any given precision and preserve the geometric features of the given curve such as the topology, singular points, etc. The approximated curve is divided into segments called quasi-cubic B\\'{e}zier curve segments which have properties similar to a cubic rational B\\'{e}zier curve. And the approximate curve is naturally constructed as the associated cubic rational B\\'{e}zier curve of the control tetrahedron of a quasi-cubic curve. A novel optimization method is proposed to select proper weights in the cubic rational B\\'{e}zier curve to approximate the given curve. The error of the approximation is controlled by the size of its tetrahedron, which converges to zero by subdividing the curve segments. As an applic...
Log-cubic method for generation of soil particle size distribution curve.
Shang, Songhao
2013-01-01
Particle size distribution (PSD) is a fundamental physical property of soils. Traditionally, the PSD curve was generated by hand from limited data of particle size analysis, which is subjective and may lead to significant uncertainty in the freehand PSD curve and graphically estimated cumulative particle percentages. To overcome these problems, a log-cubic method was proposed for the generation of PSD curve based on a monotone piecewise cubic interpolation method. The log-cubic method and commonly used log-linear and log-spline methods were evaluated by the leave-one-out cross-validation method for 394 soil samples extracted from UNSODA database. Mean error and root mean square error of the cross-validation show that the log-cubic method outperforms two other methods. What is more important, PSD curve generated by the log-cubic method meets essential requirements of a PSD curve, that is, passing through all measured data and being both smooth and monotone. The proposed log-cubic method provides an objective and reliable way to generate a PSD curve from limited soil particle analysis data. This method and the generated PSD curve can be used in the conversion of different soil texture schemes, assessment of grading pattern, and estimation of soil hydraulic parameters and erodibility factor.
On Application of Non-cubic EoS to Compositional Reservoir Simulation
DEFF Research Database (Denmark)
Yan, Wei; Michelsen, Michael Locht; Stenby, Erling Halfdan
Compositional reservoir simulation uses almost exclusively cubic equations of state (EoS) such as the SRK EoS and the PR EoS. This is in contrast with process simulation in the downstream industry where more recent and advanced thermodynamic models are quickly adopted. Many of these models are non......-cubic EoS, such as the PC-SAFT EoS. A major reason for the use of the conventional cubic EoS in reservoir simulation is the concern over computation time. Flash computation is the most time consuming part in compositional reservoir simulation, and the extra complexity of the non-cubic EoS may significantly...... such models. In this work we test the feasibility of applying a non-cubic EoS to reservoir simulation, using a slimtube simulator to simulate multicomponent gas injection using both the traditional SRK EoS and the non-cubic PC-SAFT EoS. Computation times for both models were compared. In addition, C7...
High reflected cubic cavity as long path absorption cell for infrared gas sensing
Yu, Jia; Gao, Qiang; Zhang, Zhiguo
2014-10-01
One direct and efficient method to improve the sensitivity of infrared gas sensors is to increase the optical path length of gas cells according to Beer-Lambert Law. In this paper, cubic shaped cavities with high reflected inner coating as novel long path absorption cells for infrared gas sensing were developed. The effective optical path length (EOPL) for a single cubic cavity and tandem cubic cavities were investigated based on Tunable Diode Laser Absorption Spectroscopy (TDLAS) measuring oxygen P11 line at 763 nm. The law of EOPL of a diffuse cubic cavity in relation with the reflectivity of the coating, the port fraction and side length of the cavity was obtained. Experimental results manifested an increase of EOPL for tandem diffuse cubic cavities as the decrease of port fraction of the connecting aperture f', and the EOPL equaled to the sum of that of two single cubic cavities at f'<0.01. The EOPL spectra at infrared wavelength range for different inner coatings including high diffuse coatings and high reflected metallic thin film coatings were deduced.
Origin of birefringence in common silicate garnet: intergrowth of different cubic phases
Antao, S.; Klincker, A.; Round, S.
2013-05-01
Birefringence is unexpected in ideal high symmetry cubic minerals, such as common silicate garnets. Birefringence in cubic garnet was reported over a century ago, but the origin still remains questionable. Some grossular, spessartine, andradite, and uvarovite samples may show birefringence under cross-polarized light, which may indicate that they are not optically cubic. Several reasons were given as the cause of the birefringence, but the main one appears to be cation order that may cause symmetry reduction. The crystal structure of several birefringent garnet samples (grossular, spessartine, andradite, and uvarovite) were refined by the Rietveld method, space group Ia-3d, and monochromatic synchrotron high-resolution powder X-ray diffraction (HRPXRD) data. Electron-microprobe results indicate the samples are homogeneous or non-homogenous with two or three distinct compositions. Each birefringent sample contains an assemblage of cubic phases that have slightly different unit-cell parameters. The intergrowth of different phases causes strain-induced birefringence that arises from mismatch of different cubic unit-cell parameters. These results have many implications, including garnet phase transitions from cubic to lower symmetry in the mantle, which has important geophysical consequences.
Chong, Ketpin; Tan, Olivia Li Ling; Almsherqi, Zakaria A; Lin, Qingsong; Kohlwein, Sepp D; Deng, Yuru
2015-03-01
Biological membranes with cubic symmetry are a hallmark of virus-infected or diseased cells. The mechanisms of formation and specific cellular functions of cubic membranes, however, are unclear. The best-documented cubic membrane formation occurs in the free-living giant amoeba Chaos carolinense. In that system, mitochondrial inner membranes undergo a reversible structural change from tubular to cubic membrane organization upon starvation of the organism. As a prerequisite to further analyze the structural and functional features of cubic membranes, we adapted protocols for the isolation of mitochondria from starved amoeba and have identified buffer conditions that preserve cubic membrane morphology in vitro. The requirement for high concentration of ion-chelating agents in the isolation media supports the importance of a balanced ion milieu in establishing and maintaining cubic membranes in vivo.
Pang, Maolin
2012-08-15
In this work, we carry out an investigation on shape-controlled growth of In III- and Ga III-based square-octahedral metal-organic frameworks (soc-MOFs). In particular, controllable crystal morphological evolution from simple cubes to complex octadecahedra has been achieved, and resultant highly uniform crystal building blocks promise new research opportunities for preparation of self-assembled MOF materials and related applications. © 2012 American Chemical Society.
Synthesis of Al3Fe5O12 Cubic Structure by Extremely Low Sintering Temperature of Sol Gel Technique
Directory of Open Access Journals (Sweden)
Noorhana Yahya
2009-01-01
Full Text Available Problem statement: Fabrication of nano materials particularly nano inductors at low sintering temperature remains a challenge. This study was carried out as our initial response to obtain a nano-size inductors, which is aluminium iron garnet using low sintering temperature. Approach: The aluminum iron garnet (Al3Fe5O12 nano crystals were prepared by sol-gel technique. The starting solution is a mixture of iron nitrate Fe(NO33.9H2O, yttrium nitrate Y(NO33.6H2O and aluminum nitrate Al(NO33.9H2O and were dissolved in 150 mL of citric acid, C6H8O7.H2O. The mixtures were stirred continuously, at about 250 r.p.m, in room temperature until the formation of a gel was observed. The gel was dried at 110°C in an oven to remove the unneeded water. The dried powder was calcined at 600°C, for 3 h in air and was wet crushed using a Fritsch Planetary Micromill for 6 h to obtain fine particles powder. The sample was then characterized by X-Ray Diffraction analysis (XRD to confirm the garnet phase. The sintered powder was characterized at different temperature by X-ray diffraction analysis and Raman Spectroscopy was used to study the vibration of atoms in a materials. Finally, Field Emission Scanning Electron Microscopy (FESEM was used to study the surface morphology of the sample. Results: The XRD results showed that, the best garnet cubic phase giving [1 0 4] plane of the Al3Fe5O12 crystallite appeared at 33.30 of the 2 theta. We report a clear cubic crystal structure of less than 62 nm, which was observed possible for the first time, for this type of garnet, Al3Fe5O12. The much lower sintering temperature 800°C comparing to the conventional method was attributed to the sol gel method. Conclusion: The long stirring time (one month that had allowed self assembly of the anions and cations to form the gelatin. In addition the small radius of aluminium prefers to occupy the tetrahedron and octahedron sites instead of the much larger dodecahedron site resulted to
Energy Technology Data Exchange (ETDEWEB)
Kale, Rohidas B., E-mail: rb_kale@yahoo.co.in [Department of Physics, Institute of Science, Mumbai 400032, M.S. (India); Lu, Shih-Yuan, E-mail: sylu@mx.nthu.edu.tw [Department of Chemical Engineering, National Tsing-Hua University, Hsin-Chu 30013, Taiwan (China)
2015-08-15
Highlights: • Nanocrystalline CdSe thin films were deposited using inexpensive CBD method. • Air annealing induced structural and interesting morphological transformation. • The as-deposited CdSe thin films showed a blue shift in its optical spectra. • The films showed a red shift in their optical spectra after annealing. - Abstract: CdSe thin films have been deposited onto glass substrates using a chemical bath deposition method at relatively low temperatures (40 °C). The precursors used for the deposition of the thin films are cadmium nitrate hexahydrate, freshly prepared sodium selenosulfate solution and aqueous ammonia solution as a complex as well as pH adjusting reagent. In order to study the influence of air annealing on their physicochemical properties, the as-deposited CdSe thin films were further annealed at 200 °C and 400 °C for 3 h in air atmosphere. Significant changes in the morphology and photonic properties were clearly observed after the thermal annealing of the CdSe thin films. The as-deposited CdSe films grow with the cubic phase that transforms into mixed cubic and hexagonal wurtzite phase with improved crystalline quality of the films after the air annealing. Morphological observation reveals that the as-deposited thin films grow with multilayer that consists of network or mesh like structure, uniformly deposited on the glass substrate over which microspheres are uniformly distributed. After air annealing, CdSe nanorods emerged from the microspheres along with conversion of few microspheres into micro-pyramids. The UV–visible study illustrates that the as-deposited thin film shows blue shifts in its optical spectrum and the spectrum was red-shifted after annealing the CdSe thin films. The band gap of the CdSe thin films were found to be decreased after the thermal treatment.
Cubic Yb3+-activated Y6MoO12 micro-powder - optical material operating in NIR region
Bieza, M.; Guzik, M.; Tomaszewicz, E.; Guyot, Y.; Boulon, G.
2017-01-01
We present Yb3+-doped Y6MoO12 solid solutions as a very promising NIR emitting phosphor with some hope to obtain them in the nearest future in the form of transparent ceramics due to their cubic structure. The samples are crystallizing in the cubic system with the space group Fm-3m. To perform a full structural and spectroscopic analysis on the well crystallized samples they were obtained in the uniform micro-crystal forms. The ternary Y6MoO12 and Yb3+-doped Y6MoO12 solid solutions containing a large concentration range of activator (0.1, 1, 3, 5, 10, 20 mol%) have been prepared by a high-temperature solid-state reaction method using the Yb2O3/Y2O3/MoO3 mixtures annealed in the air in the temperature range of 550-1550 °C for 6 h. As-obtained samples were systematically characterized by the X-ray powder diffraction (XRD), scanning electron microscopy (SEM), UV-Vis-NIR reflectance. Furthermore, to check the thermal stability of these molybdates the thermogravimetric analysis have been performed. Finally, the luminescent properties of Yb3+ ions activated Y6MoO12 microcrystals were investigated by using the high resolution absorption and emission techniques including the site selective spectroscopy at room and low temperatures. Basing on the absorption and emission spectra the Yb3+ electronic energy levels diagram has been proposed for the main site. The concentration quenching mechanism of Yb3+ ion in this host lattice was also discussed. Obtained results have demonstrated that Yb3+-doped Y6MoO12 microcrystals exhibited good luminescent properties and possess many advantages compared to other compounds based on molybdates and might have potential applications in the laser technology.
Reactive Mechanical Alloying Synthesis of Nanocrystalline Cubic Zirconium Nitride
Institute of Scientific and Technical Information of China (English)
QIU Li-Xia; YAO Bin; DING Zhan-Hui; ZHAO Xu-Dong; JI Hong; DU Xiao-Bo; JIA Xiao-Peng; ZHENG Wei-Tao
2008-01-01
Zirconium nitride powders with rock salt structure (γ-ZrNx) are prepared by mechanical milling of a mixture of Zirconium and hexagonal boron nitride (h-BN) powders.The products are analysed by x-ray diffraction (XRD),scanning electron microscopy (SEM),and Raman spectroscopy (RS).The formation mechanism of γ-ZrNx by ball milling technique is investigated in detail.N atoms diffuse from amorphous BN (a-BN) into Zr to form Zr(N) solid solution alloy,then the Zr(N) solid solution alloy decomposes into γ-ZrNx.No ZrB2 is observed in the as-milled samples or the samples annealed at 1050℃ for 2 h.
Nanotwin hardening in a cubic chromium oxide thin film
Directory of Open Access Journals (Sweden)
Kazuma Suzuki
2015-09-01
Full Text Available NaCl-type (B1 chromium oxide (CrO has been expected to have a high hardness value and does not exist as an equilibrium phase. We report a B1-based Cr0.67O thin film with a thickness of 144 nm prepared by pulsed laser deposition as an epitaxial thin film on a MgO single crystal. The thin film contained a number of stacking faults and had a nanotwinned structure composed of B1 with disordered vacancies and corundum structures. The Cr0.67O thin film had a high indentation hardness value of 44 GPa, making it the hardest oxide thin film reported to date.
Characterizations of Cubic ZnMgO Films Grown on Si(111) at Low Substrate Temperature
Institute of Scientific and Technical Information of China (English)
邱东江; 吴惠桢; 陈乃波; 徐天宁
2003-01-01
Cubic ZnMgO thin films in the (100) orientation were grown on Si (111) substrates by reactive electron beamevaporation at low substrate temperature. X-ray photoelectron spectroscopy (XPS) analyses show that Mgcontent as high as 75 at.% in the cubic ZnMgO film can be obtained. Secondary ion mass spectroscopy (SIMS)measurement indicates the evidence of Mg richness in the interface between the ZnMgO film and the Si substrate,and it is probably the primary reason to form the MgO-like cubic ZnMgO structures rather than the wurtziteone. The optical band gap of cubic ZnMgO is estimated to be 5.76eV, which was measured by the transmissionspectrum of the cubic ZnMgO film grown on the sapphire substrate under the same growth condition with thaton Si (111). The band gap is of 2.39eV blueshifted compared with that of ZnO (3.37eV), which should renderapplications in the fabrication of ZnMgO-related heterostructures.
Structural Characterization of Cubic GaN Grown on GaAs(001) Substrates
Institute of Scientific and Technical Information of China (English)
ZHENG Xinhe; QU Bo; WANG Yutian; YANG Hui; LIANGJunwu; HAN Jingyi
2001-01-01
Structural characteristics of cubic GaN epilayers grown on GaAs(001) were studied using X-ray double-crystal diffraction technique. The structure factors of cubic GaN(002) and (004) components are approximately identical. However, the integrated intensities of the rocking curve for cubic (002) components are over five times as those of (004)components. The discrepancy has been interpreted in detail considering other factors. In the conventional double crystal rocking curve, the peak broadening includes such information caused by the orientation distribution (mosaicity) and the distribution of lattice spacing. These two kinds of distributions can be distinguished by the triple-axis diffraction in which an analyzer crystal is placed in front of the detector.Moreover, the peak broadening was analyzed by reciprocal lattice construction and Eward sphere. By using triple-axis diffraction of cubic (002) and (113)components, domain size and dislocation density were estimated. The fully relaxed lattice parameter of cubic GaN was determined to be about 0.451 ± 0.001nm.
Kudryavtsev, Y. V.; Perekos, A. E.; Uvarov, N. V.; Kolchiba, M. R.; Synoradzki, K.; Dubowik, J.
2016-05-01
Magnetic and transport properties of near stoichiometric metastable FexMnyGaz alloys (46 ≤ x ≤ 52, 17 ≤ y ≤ 25, 26 ≤ z ≤ 30) with face-centered cubic (FCC), body-centered cubic (BCC), and two-phase (FCC + BCC) structures are investigated. The experimental results are analyzed in terms of first-principles calculations of stoichiometric Fe2MnGa alloy with the L21, L12, and the tetragonally distorted L21 structural orderings. It is shown that the pure BCC and FCC phases have distinct magnetic and transport properties. Two-phase Fe2MnGa alloys have magnetic and transport properties typical of the mixed BCC and FCC phases. Among the investigated alloys, Fe46Mn24Ga30 has a martensitic transformation accompanied with significant changes of its magnetic and transport properties.
Cubic Form of Pb_{2-x}Sn_{x}S_{2} Stabilized through Size Reduction to the Nanoscale
Energy Technology Data Exchange (ETDEWEB)
Soriano, Ronald B; Malliakas, Christos D; Wu, Jinsong; Kanatzidis, Mercouri G [NWU
2012-04-02
We demonstrate the synthesis of semiconductor Pb_{2-x}Sn_{x}S_{2} nanocrystals with a cubic rock salt crystal structure in a composition range where this structure is unstable in the bulk. The cubic Pb_{2-x}Sn_{x}S_{2} nanocrystals were prepared using a modified hot injection colloidal synthetic route. The x value is in the range 0.40 < x < 1. Even though these compositions lie in a region of the PbS-SnS phase diagram where no single phase exists, and despite the fact that PbSnS_{2} is a distorted orthorhombic phase, the Pb_{2-x}Sn_{x}S_{2} nanocrystals are single phase solid solutions with cubic NaCl-type structure. Experimental evidence for this derives from powder X-ray diffraction (PXRD), electron diffraction, and pair distribution function (PDF) analysis. Elemental compositions determined using scanning transmission electron microscopy/energy dispersive spectroscopy (STEM/EDS), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), and electron energy loss spectroscopy (EELS) reveal a composition close to the nominal ones. The band gaps of the Pb_{2-x}Sn_{x}S_{2} nanocrystals (0.52-0.57 eV) are blue-shifted by quantum confinement relative to that of the hypothetical cubic PbSnS2 phase which density functional theory (DFT) calculations show to be much narrower (0.2 eV) than in the case of orthorhombic PbSnS_{2} (1.1 eV). The Pb_{2-x}Sn_{x}S_{2} nanocrystals exhibit a well-defined band gap in the near-IR region and are stable up to 300 °C above which they phase separate into cubic PbS and orthorhombic α-SnS.
Energy Technology Data Exchange (ETDEWEB)
Sveinbjörnsson, Dadi; Blanchard, Didier [Department of Energy Conversion and Storage, Technical University of Denmark, Frederiksborgvej 399, P.O. Box 49, DK-4000 Roskilde (Denmark); Myrdal, Jon Steinar Gardarsson [Department of Energy Conversion and Storage, Technical University of Denmark, Frederiksborgvej 399, P.O. Box 49, DK-4000 Roskilde (Denmark); Center for Atomic-Scale Materials Design, Department of Physics, Technical University of Denmark, Anker Engelunds Vej 1, DK-2800 Lyngby (Denmark); Younesi, Reza; Viskinde, Rasmus [Department of Energy Conversion and Storage, Technical University of Denmark, Frederiksborgvej 399, P.O. Box 49, DK-4000 Roskilde (Denmark); Riktor, Marit Dalseth [Physics Department, Institute for Energy Technology, Instituttveien 18, P.O. Box 40, NO-2027 Kjeller (Norway); Norby, Poul [Department of Energy Conversion and Storage, Technical University of Denmark, Frederiksborgvej 399, P.O. Box 49, DK-4000 Roskilde (Denmark); Vegge, Tejs, E-mail: teve@dtu.dk [Department of Energy Conversion and Storage, Technical University of Denmark, Frederiksborgvej 399, P.O. Box 49, DK-4000 Roskilde (Denmark)
2014-03-15
LiBH{sub 4}–Ca(BH{sub 4}){sub 2} composites were prepared by ball milling. Their crystal structures and phase composition were investigated using synchrotron X-ray diffraction and Rietveld refinement, and their ionic conductivity was measured using impedance spectroscopy. The materials were found to form a physical mixture. The composites were composed of α-Ca(BH{sub 4}){sub 2}, γ-Ca(BH{sub 4}){sub 2} and orthorhombic LiBH{sub 4}, and the relative phase quantities of the Ca(BH{sub 4}){sub 2} polymorphs varied significantly with LiBH{sub 4} content. The formation of small amounts of orthorhombic CaH{sub 2} and cubic CaH{sub 2} in a CaF{sub 2}-like structure was observed upon heat treatment. Concurrent formation of elemental boron may also occur. The ionic conductivity of the composites was measured using impedance spectroscopy, and was found to be lower than that of ball milled LiBH{sub 4}. Electronic band structure calculations indicate that cubic CaH{sub 2} with hydrogen defects is electronically conducting. Its formation along with the possible precipitation of boron therefore has an effect on the measured conductivity of the LiBH{sub 4}–Ca(BH{sub 4}){sub 2} composites and may increase the risk of an internal short-circuit in the cells. -- Graphical abstract: An Arrhenius plot of the ionic conductivity of the LiBH{sub 4}–Ca(BH{sub 4}){sub 2} composites (red, blue, green). The ionic conductivity of ball milled (gray) and non-milled (black) LiBH{sub 4} is shown for comparison. The filled symbols are measured during heating runs and the empty symbols are measured during subsequent cooling runs. The conductivity of the composites is in all cases higher during cooling, most probably due to the formation of an electronically conducting layer containing defect-rich cubic CaH{sub 2}. Such layer formation could eventually lead to a short circuit in the cell and reveals a general issue of chemical stability that should be attended to in the development of solid
Directory of Open Access Journals (Sweden)
Xiaolong Wang
2013-01-01
Full Text Available In general, proper orthogonal decomposition (POD method is used to deal with single-parameter problems in engineering practice, and the linear interpolation is employed to establish the reduced model. Recently, this method is extended to solve the double-parameter problems with the amplitudes being achieved by cubic B-spline interpolation. In this paper, the accuracy of reduced models, which are established with linear interpolation and cubic B-spline interpolation, respectively, is verified via two typical examples. Both results of the two methods are satisfying, and the results of cubic B-spline interpolation are more accurate than those of linear interpolation. The results are meaningful for guiding the application of the POD interpolation to complex multiparameter problems.
On the magnetization process and the associated probability in anisotropic cubic crystals
Khedr, D. M.; Aly, Samy H.; Shabara, Reham M.; Yehia, Sherif
2017-05-01
We present a theoretical method to calculate specific magnetic properties, e.g. magnetization curves, magnetic susceptibility and probability landscapes along the [100], [110] and [111] crystallographic directions of a crystal of cubic symmetry. The probability landscape displays the evolution of the most probable angular orientation of the magnetization vector, for selected temperatures and magnetic fields. Our method is based on the premises of classical statistical mechanics. The energy density, used in the partition function, is the sum of magnetic anisotropy and Zeeman energies, however no other energies e.g. elastic or magnetoelastic terms are considered in the present work. Model cubic systems of diverse anisotropies are analyzed first, and subsequently material magnetic systems of cubic symmetry; namely iron, nickel and Cox Fe100-x compounds, are discussed. We highlight a correlation between magnetization curves and the associated probability landscapes. In addition, determination of easiest axes of magnetization, using energy consideration, is done and compared with the results of the present method.
Directory of Open Access Journals (Sweden)
A. Beléndez
2012-01-01
Full Text Available Accurate approximate closed-form solutions for the cubic-quintic Duffing oscillator are obtained in terms of elementary functions. To do this, we use the previous results obtained using a cubication method in which the restoring force is expanded in Chebyshev polynomials and the original nonlinear differential equation is approximated by a cubic Duffing equation. Explicit approximate solutions are then expressed as a function of the complete elliptic integral of the first kind and the Jacobi elliptic function cn. Then we obtain other approximate expressions for these solutions, which are expressed in terms of elementary functions. To do this, the relationship between the complete elliptic integral of the first kind and the arithmetic-geometric mean is used and the rational harmonic balance method is applied to obtain the periodic solution of the original nonlinear oscillator.
Pressure-induced phase transformations in cubic Gd[subscript 2]O[subscript 3
Energy Technology Data Exchange (ETDEWEB)
Bai, Ligang; Liu, Jing; Li, Xiaodong; Jiang, Sheng; Xiao, Wansheng; Li, Yanchun; Tang, Lingyun; Zhang, Yufeng; Zhang, Dechun; (Chinese Aca. Sci.)
2009-10-21
High-pressure transformation and compression behavior of Gd{sub 2}O{sub 3} were investigated using synchrotron radiation x-ray diffraction in a diamond anvil cell up to 44 GPa at room temperature. The structural transformation from a cubic to a monoclinic phase occurred during the sample precompression process. Phase transitions from both the cubic and the monoclinic polymorphs to a hexagonal structure were observed. The hexagonal phase was stable up to the highest pressure in this study and was not quenchable and transformed to a monoclinic phase after pressure release. The bulk moduli of Gd{sub 2}O{sub 3} for the cubic, monoclinic, and hexagonal phases were obtained by fitting the compression data to the Birch-Murnaghan equation of state. Moreover, an anomaly of the hexagonal type Gd{sub 2}O{sub 3} was observed.
Cubic one-regular graphs of order twice a square-free integer
Institute of Scientific and Technical Information of China (English)
2008-01-01
A graph is one-regular if its automorphism group acts regularly on the set of its arcs.Let n be a square-free integer.In this paper,we show that a cubic one-regular graph of order 2n exists if and only if n=3tp1p2…ps≥13,where t≤1,s≥1 and pi’s are distinct primes such that 3|（Pi—1）. For such an integer n,there are 2s-1 non-isomorphic cubic one-regular graphs of order 2n,which are all Cayley graphs on the dihedral group of order 2n.As a result,no cubic one-regular graphs of order 4 times an odd square-free integer exist.
Baena, J D; Marques, R
2007-01-01
In this paper a systematic approach to the design of bulk isotropic magnetic metamaterials is presented. The role of the symmetries of both the constitutive element and the lattice are analyzed. For this purpose it is assumed that the metamaterial is composed by cubic SRR resonators, arranged in a cubic lattice. The minimum symmetries needed to ensure an isotropic behavior are analyzed, and some particular configurations are proposed. Besides, an equivalent circuit model is proposed for the considered cubic SRR resonators. Experiments are carried out in order to validate the proposed theory. We hope that this analysis will pave the way to the design of bulk metamaterials with strong isotropic magnetic response, including negative permeability and left-handed metamaterials.
Pivotal surfaces in inverse hexagonal and cubic phases of phospholipids and glycolipids.
Marsh, Derek
2011-03-01
Data on the location and dimensions of the pivotal surfaces in inverse hexagonal (H(II)) and inverse cubic (Q(II)) phases of phospholipids and glycolipids are reviewed. This includes the H(II) phases of dioleoyl phosphatidylethanolamine, 2:1 mol/mol mixtures of saturated fatty acids with the corresponding diacyl phosphatidylcholine, and glucosyl didodecylglycerol, and also the Q(II)(230/G) gyroid inverse cubic phases of monooleoylglycerol and glucosyl didodecylglycerol. Data from the inverse cubic phases are largely compatible with those from inverse hexagonal H(II)-phases. The pivotal plane is located in the hydrophobic region, relatively close to the polar-apolar interface. The area per lipid at the pivotal plane is similar in size to lipid cross-sectional areas found in the fluid lamellar phase (L(α)) of lipid bilayers. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.
The structure model of a cubic aperiodic phase ('quasicrystal without forbidden symmetry axes').
Kraposhin, V S; Talis, A L; Thanh Lam, Ha
2008-03-19
A model structure of the aperiodic cubic phase (a cubic quasicrystal) has been constructed as a periodical packing of hierarchical octahedral clusters which were composed of truncated tetrahedra (Friauf-Laves polyhedra) and chains of Frank-Kasper polyhedra with 14 vertices. The construction of the hierarchical model for the cubic aperiodic phase became possible due to the discovery of a new space subdivision with equal edges and with vertices belonging to two orbits of the space group Fm3m. The subdivision is characterized by unique values and unique relations between the coordinates of the starting points of two orbits. Calculated x-ray diffraction patterns for the proposed hierarchical model are in qualitative agreement with published experimental x-ray patterns for aperiodical phases observed in melt-quenched Mg-Al and Fe-Nb-B-Si alloys.
Formation Mechanism and Binding Energy for Body-Centered Cubic Structure of He+9 Cluster
Institute of Scientific and Technical Information of China (English)
ZHANG Jian-Ping; GOU Qing-Quan; LI Ping
2004-01-01
The formation mechanism for the body-centered cubic structure of He+9 cluster is proposed and its total energy curve is calculated by the method of a Modified Arrangement Channel Quantum Mechanics. The energy is the function of separation R between the nuclei at the center and an apex of the body-centered cubic structure. The result of the calculation shows that the curve has a minimal energy -25.6669 (a.u.) at R = 2.550ao. The binding energy of He+9 with respect to He+ + 8He was calculated to be 0.8857 a.u. This means that the cluster of He+9 may be formed in the body-centered cubic structure of R = 2.55a0.
Interaction in equilibrium plasmas of charged macroparticles located in nodes of cubic lattices
Filippov, A. V.
2016-11-01
Interaction of two charged pointlike macroparticles located at nodes of simple cubic (sc), body-centered cubic (bcc) and face-centered cubic (fcc) lattices in an equilibrium plasma is studied within the linearized Poisson-Boltzmann model. It is shown that the boundary shape has a strong influence on the electrostatic interaction between two macroparticles, which switches from repulsion at small interparticle distances to attraction as it approaches the halflength of a computational cell. It is found that in a case of dust particles arranged in the nodes of the sc, bcc and fcc lattices, the electrostatic force acting on them is equal to zero and the nature of the interaction changes from repulsion to attraction; hence, the infinite sc, bcc and fcc lattices of charged dust particles are thermodynamically stable at rather low temperatures.
Effect of pressure on itinerant magnetism and spin disorder in cubic FeGe.
Pulikkotil, J J; Auluck, S; Rout, P K; Budhani, R C
2012-03-01
The results of ab initio calculations of the pressure dependence of Fe magnetism in cubic FeGe are presented. We find that when the pressure-volume scale is set by means of generalized gradient approximation total energies and magnetism is described by means of the local density approximation, the critical pressure at which the magnetic phase transition occurs is estimated at ≈18 GPa, which is in good agreement with experiments. Using the disordered local moment method we find a localized to itinerant model cross-over of Fe magnetism in cubic FeGe, as a function of volume. Moreover, our calculations also suggest subtle signatures of longitudinal spin fluctuations in cubic FeGe, and that the stiffness parameter softens with increasing pressure. We associate the retention of metallicity in FeGe under pressure with the spin-disorder scattering. The effect of spin-orbit coupling on the electronic structure is also discussed.
Direct visualization of dispersed lipid bicontinuous cubic phases by cryo-electron tomography
Demurtas, Davide; Guichard, Paul; Martiel, Isabelle; Mezzenga, Raffaele; Hébert, Cécile; Sagalowicz, Laurent
2015-11-01
Bulk and dispersed cubic liquid crystalline phases (cubosomes), present in the body and in living cell membranes, are believed to play an essential role in biological phenomena. Moreover, their biocompatibility is attractive for nutrient or drug delivery system applications. Here the three-dimensional organization of dispersed cubic lipid self-assembled phases is fully revealed by cryo-electron tomography and compared with simulated structures. It is demonstrated that the interior is constituted of a perfect bicontinuous cubic phase, while the outside shows interlamellar attachments, which represent a transition state between the liquid crystalline interior phase and the outside vesicular structure. Therefore, compositional gradients within cubosomes are inferred, with a lipid bilayer separating at least one water channel set from the external aqueous phase. This is crucial to understand and enhance controlled release of target molecules and calls for a revision of postulated transport mechanisms from cubosomes to the aqueous phase.
Engl, K; Zweck, J
2002-01-01
Rare-earth/iron multilayered thin films were magnetron sputtered to investigate the thickness-dependent transition from amorphous iron to polycrystalline body-centred-cubic iron. To characterize this transition it is necessary to get information about the average short-range order (SRO) in the multilayers. A unique technique for measuring this SRO is calculating pair distribution functions (PDFs) from reduced intensity functions by using high-energy electron diffraction in a 300 kV transmission electron microscope. With a maximum resolution in the PDFs of 0.024 nm, this method offers a high sensitivity for the investigation of the SRO. Due to the planar probing characteristics of the experiment, one gets structure information on interfaces rather than from the bulk structure. A further advantage of this method is that no specimen preparation is necessary. Therefore preparation artefacts can be excluded.
Epitaxial and bulk growth of cubic silicon carbide on off-oriented 4H-silicon carbide substrates
Norén, Olof
2015-01-01
The growth of bulk cubic silicon carbide has for a long time seemed to be something for the future. However, in this thesis the initial steps towards bulk cubic silicon carbide have been taken. The achievement of producing bulk cubic silicon carbide will have a great impact in various fields of science and industry such as for example the fields of semiconductor technology within electronic- and optoelectronic devices and bio-medical applications. The process that has been used to grow the bu...
Synthesis of Nano-Scale Fast Ion Conducting Cubic Li7La3Zr2O12
2013-09-25
0.24 moles of aluminum was added using aluminum oxide (50 nm, Merck) to the precursor solution before gelation occurs. The process flow diagram...cubic Li A solution-based process was investigated for synthesizing cubic Li7La3Zr2O12 (LLZO), which is known to exhibit the unprecedented combination of...Park, NC 27709-2211 batteries, solution based process , synthesizing cubic LLZO, fast ionic conductivity REPORT DOCUMENTATION PAGE 11. SPONSOR
Drag force in bimodal cubic-quintic nonlinear Schr\\"odinger equation
Feijoo, David; Paredes, Ángel; Michinel, Humberto
2016-01-01
We consider a system of two cubic-quintic non-linear Schr\\"odinger equations in two dimensions, coupled by repulsive cubic terms. We analyse situations in which a probe lump of one of the modes is surrounded by a fluid of the other one and analyse their interaction. We find a realization of D'Alembert's paradox for small velocities and non-trivial drag forces for larger ones. We present numerical analysis including the search of static and traveling form-preserving solutions along with simulations of the dynamical evolution in some representative examples.
Analysis of moderately thin-walled beam cross-sections by cubic isoparametric elements
DEFF Research Database (Denmark)
Høgsberg, Jan Becker; Krenk, Steen
2014-01-01
numerically by introducing a cubic-linear two-dimensional isoparametric element. The cubic interpolation of this element accurately represents quadratic shear stress variations along cross-section walls, and thus moderately thin-walled cross-sections are effectively discretized by these elements. The ability......In technical beam theory the six equilibrium states associated with homogeneous tension, bending, shear and torsion are treated as individual load cases. This enables the formulation of weak form equations governing the warping from shear and torsion. These weak form equations are solved...... of this element to represent curved geometries, and to accurately determine cross-section parameters and shear stress distributions is demonstrated....
1:2 INTERNAL RESONANCE OF COUPLED DYNAMIC SYSTEM WITH QUADRATIC AND CUBIC NONLINEARITIES
Institute of Scientific and Technical Information of China (English)
陈予恕; 杨彩霞; 吴志强; 陈芳启
2001-01-01
The 1:2 internal resonance of coupled dynamic system with quadratic and cubic nonlinearities is studied. The normal forms of this system in 1: 2 internal resonance were derived by using the direct method of normal form. In the normal forms, quadratic and cubic nonlinearities were remained. Based on a new convenient transformation technique, the 4-dimension bifurcation equations were reduced to 3-dimension. A bifurcation equation with one-dimension was obtained. Then the bifurcation behaviors of a universal unfolding were studied by using the singularity theory. The method of this paper can be applied to analyze the bifurcation behavior in strong internal resonance on 4-dimension center manifolds.
Cubic B-Spline Collocation Method for One-Dimensional Heat and Advection-Diffusion Equations
Directory of Open Access Journals (Sweden)
Joan Goh
2012-01-01
Full Text Available Numerical solutions of one-dimensional heat and advection-diffusion equations are obtained by collocation method based on cubic B-spline. Usual finite difference scheme is used for time and space integrations. Cubic B-spline is applied as interpolation function. The stability analysis of the scheme is examined by the Von Neumann approach. The efficiency of the method is illustrated by some test problems. The numerical results are found to be in good agreement with the exact solution.
GA Based Rational cubic B-Spline Representation for Still Image Interpolation
Directory of Open Access Journals (Sweden)
Samreen Abbas
2016-12-01
Full Text Available In this paper, an image interpolation scheme is designed for 2D natural images. A local support rational cubic spline with control parameters, as interpolatory function, is being optimized using Genetic Algorithm (GA. GA is applied to determine the appropriate values of control parameter used in the description of rational cubic spline. Three state-of-the-art Image Quality Assessment (IQA models with traditional one are hired for comparison with existing image interpolation schemes and perceptual quality check of resulting images. The results show that the proposed scheme is better than the existing ones in comparison.
Optical properties of GaAs 2D hexagonal and cubic photonic crystal
Energy Technology Data Exchange (ETDEWEB)
Arab, F., E-mail: farab@CDTA.DZ; Assali, A.; Grain, R.; Kanouni, F. [Centre for Development of Advanced Technologies (CDTA) Research Unit in Optics and Photonics (UROP), University of Setif 1, El Bez, 19000 Setif (Algeria)
2015-03-30
In this paper we present our theoretical study of 2D hexagonal and cubic rods GaAs in air, with plan wave expansion (PWE) and finite difference time domain (FDTD) by using BandSOLVE and FullWAVE of Rsoft photonic CAD package. In order to investigate the effect of symmetry and radius, we performed calculations of the band structures for both TM and TE polarization, contour and electromagnetic propagation and transmission spectra. Our calculations show that the hexagonal structure gives a largest band gaps compare to cubic one for a same filling factor.
Investigation of Cubic EOS Models for HFO-1234yf Refrigerant Used In Automotive application
Agrawal, Anant; Cornelio, Avi Anthony; Limperich, Dirk
2012-01-01
The need for a consistent and reliable calculation of thermodynamic property of refrigerants has been a topic of research since the past decade. This paper reports a study of various cubic equations of state (EOS) for a refrigerant to be used in automotive applications. Thermodynamic properties of refrigerant 2,3,3,3-tetrafluoropropene (HFO- 1234yf) using three different cubic equations of state, i.e. Peng-Robinson (PR), Yu-Lu (YL) and Guo-Du (GD), are modeled, compared and analyzed. A generi...
Recurrence approach and higher rank cubic algebras for the N-dimensional superintegrable systems
Fazlul Hoque, Md; Marquette, Ian; Zhang, Yao-Zhong
2016-03-01
By applying the recurrence approach and coupling constant metamorphosis, we construct higher order integrals of motion for the Stackel equivalents of the N-dimensional superintegrable Kepler-Coulomb model with non-central terms and the double singular oscillators of type (n,N-n). We show how the integrals of motion generate higher rank cubic algebra C(3)\\oplus {L}1\\oplus {L}2 with structure constants involving Casimir operators of the Lie algebras L 1 and L 2. The realizations of the cubic algebras in terms of deformed oscillators enable us to construct finite dimensional unitary representations and derive the degenerate energy spectra of the corresponding superintegrable systems.
Equation of state for charge-doping-induced deformation and hardening in cubic crystals
Li, Yao; Liu, Xiaofei; Guo, Wanlin
2017-08-01
Charge doping would inevitably induce strain, which can significantly influence device performance but cannot be directly predicted by classical mechanical laws. Here we present a set of equations of states for deformable cubic crystals subjected to charge doping by introducing the quantum electronic stress at fixed lattice as equivalent mechanical pressure into the classical hydrostatic pressure-vs-deformation equations. The equations are proved to be efficient for all the cubic crystals considered in this work (diamond, Si, Ge, GaAs, Al, and ZrO2) by first-principles calculations. The proposed method and presented equations should pave a convenient way to predict doping effects on device performance.
Ising low-temperature polynomials and hard-sphere gases on cubic lattices of general dimension
Butera, P
2015-01-01
We derive and analyze the low-activity and low-density expansions of the pressure for the model of a hard-sphere gas on cubic lattices of general dimension $d$, through the 13th order. These calculations are based on our recent extension to dimension d of the low-temperature expansions for the specific free-energy of the spin-1/2 Ising models subject to a uniform magnetic field on the (hyper-)simple-cubic lattices. Estimates of the model parameters are given also for some other lattices
Ferrighi, Lara; Frediani, Luca; Ruud, Kenneth
2010-01-01
The theory and an implementation of the solvent contribution to the cubic response function for the polarizable continuum model for multiconfigurational self-consistent field wave functions is presented. The excited-state polarizability of benzene, para-nitroaniline, and nitrobenzene has been obtained from the double residue of the cubic response function calculated in the presence of an acetonitrile and dioxane solvent. The calculated excited-state polarizabilities are compared to results obtained from the linear response function of the explicitly optimized excited states.
Connected cubic s-arc-regular Cayley graphs of finite nonabelian simple groups
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
A graph is said to be s-arc-regular if its full automorphism group acts regularly on the set of its s-arcs. In this paper, we investigate connected cubic s-arc-regular Cayley graphs of finite nonabelian simple groups. Two suffcient and necessary conditions for such graphs to be 1- or 2-arc-regular are given and based on the conditions, several infinite families of 1-or 2-arc-regular cubic Cayley graphs of alternating groups are constructed.
Spinor-Helicity Three-Point Amplitudes from Local Cubic Interactions
Conde, Eduardo; Mkrtchyan, Karapet
2016-01-01
We make an explicit link between the cubic interactions of off-shell fields and the on-shell three-point amplitudes in four dimensions. Both the cubic interactions and the on-shell three-point amplitudes had been independently classified in the literature, but their relation has not been made explicit. The aim of this note is to provide such a relation and discuss similarities and differences of their constructions. For the completeness of our analysis, we also derive the covariant form of all parity-odd massless vertices.
Finite Element Treatment of Vortex States in 3D Cubic Superconductors in a Tilted Magnetic Field
Peng, Lin; Cai, Chuanbing
2017-03-01
The time-dependent Ginzburg-Landau equations have been solved numerically by a finite element analysis for superconducting samples with a cubic shape in a tilted magnetic field. We obtain different vortex patterns as a function of the external magnetic field. With a magnetic field not parallel to the x- or y-axis, the vortices attempt to change their orientation accordingly. Our analysis of the corresponding changes in the magnetic response in different directions can provide information not only about vorticity but also about the three-dimensional vortex arrangement, even about the very subtle changes for the superconducting samples with a cubic shape in a tilted magnetic field.
Energy Technology Data Exchange (ETDEWEB)
Stalin, S. [Centre for Nonlinear Dynamics, School of Physics, Bharathidasan University, Tiruchirappalli 620024, Tamil Nadu (India); Senthilvelan, M., E-mail: velan@cnld.bdu.ac.in [Centre for Nonlinear Dynamics, School of Physics, Bharathidasan University, Tiruchirappalli 620024, Tamil Nadu (India)
2011-10-17
In this Letter, we formulate an exterior differential system for the newly discovered cubically nonlinear integrable Camassa-Holm type equation. From the exterior differential system we establish the integrability of this equation. We then study Cartan prolongation structure of this equation. We also discuss the method of identifying conservation laws and Baecklund transformation for this equation from the identified exterior differential system. -- Highlights: → An exterior differential system for a cubic nonlinear integrable equation is given. → The conservation laws from the exterior differential system is derived. → The Baecklund transformation from the Cartan-Ehresmann connection is obtained.
Limit cycles from a cubic reversible system via the third-order averaging method
Directory of Open Access Journals (Sweden)
Linping Peng
2015-04-01
Full Text Available This article concerns the bifurcation of limit cycles from a cubic integrable and non-Hamiltonian system. By using the averaging theory of the first and second orders, we show that under any small cubic homogeneous perturbation, at most two limit cycles bifurcate from the period annulus of the unperturbed system, and this upper bound is sharp. By using the averaging theory of the third order, we show that two is also the maximal number of limit cycles emerging from the period annulus of the unperturbed system.
Cubic systems with invariant affine straight lines of total parallel multiplicity seven
Directory of Open Access Journals (Sweden)
Alexandru Suba
2013-12-01
Full Text Available In this article, we study the planar cubic differential systems with invariant affine straight lines of total parallel multiplicity seven. We classify these system according to their geometric properties encoded in the configurations of invariant straight lines. We show that there are only 17 different topological phase portraits in the Poincar\\'e disc associated to this family of cubic systems up to a reversal of the sense of their orbits, and we provide representatives of every class modulo an affine change of variables and rescaling of the time variable.
Preconditioning cubic spline collocation method by FEM and FDM for elliptic equations
Energy Technology Data Exchange (ETDEWEB)
Kim, Sang Dong [KyungPook National Univ., Taegu (Korea, Republic of)
1996-12-31
In this talk we discuss the finite element and finite difference technique for the cubic spline collocation method. For this purpose, we consider the uniformly elliptic operator A defined by Au := -{Delta}u + a{sub 1}u{sub x} + a{sub 2}u{sub y} + a{sub 0}u in {Omega} (the unit square) with Dirichlet or Neumann boundary conditions and its discretization based on Hermite cubic spline spaces and collocation at the Gauss points. Using an interpolatory basis with support on the Gauss points one obtains the matrix A{sub N} (h = 1/N).
Industrial growth of yttria-stabilized cubic zirconia crystals by skull melting process
Institute of Scientific and Technical Information of China (English)
徐家跃; 雷秀云; 蒋新; 何庆波; 房永征; 张道标; 何雪梅
2009-01-01
We reported the development of a Ф100 cm growth apparatus for skull melting growth of yttria-stabilized cubic zirconia(YSZ) crystals and more than 1000 kg crystals have been grown in the furnace each time.The growth conditions were optimized and the structure of the as-grown crystals was characterized by X-ray diffraction.The transmittance of 15 mol.% yttria-stabilized cubic zirconia crystal was nearly 80% in the range of 400-1600 nm.The refractive indices were measured and fitted the Sellmeier equation whi...
Lee, Jin-Yeon; Kwak, Da-Hee; Lee, Young-Woo; Lee, Seul; Park, Kyung-Won
2015-04-14
The electrocatalytic properties for electro-oxidation reactions of shape-controlled Pt-based catalysts have been improved by alloying with 2nd elements. In this study, we demonstrate cubic PtPd alloy nanoparticles synthesized using a thermal decomposition method. The cubic PtPd nanoparticles exhibit a homogeneous distribution of alloy nanostructures in the presence of Pt and Pd metallic phases. The improved electrocatalytic activity for the electro-oxidation reactions of methanol and formic acid as chemical fuels might be attributed to the cubic alloy nanostructures. Furthermore, the cubic PtPd alloy nanoparticles as electrocatalysts exhibit excellent stability for electro-oxidation reactions.
Peng, R.; Lin, C.K.; Baltrusaitis, Jonas; Wu, C.M.; Dimitrijevic, N.M.; Rajh, T.; May, S.; Koodali, R.T.
2014-01-01
CdS incorporated Si-MCM-48 and Ti-MCM-48 cubic phased mesoporous photocatalysts were prepared by a two-step modification synthetic approach under relatively mild conditions. A highly efficient (24.8%, apparent quantum yield (AQY)) photocatalyst for visible light (λ > 400 nm) enabled solar hydrogen
Peng, R.; Lin, C.K.; Baltrusaitis, J.; Wu, C.M.; Dimitrijevic, N.M.; Rajh, T.; May, S.; Koodali, R.T.
2014-01-01
CdS incorporated Si-MCM-48 and Ti-MCM-48 cubic phased mesoporous photocatalysts were prepared by a two-step modification synthetic approach under relatively mild conditions. A highly efficient (24.8%, apparent quantum yield (AQY)) photocatalyst for visible light (λ > 400 nm) enabled solar hydrogen e
Energy Technology Data Exchange (ETDEWEB)
Seitz, M.G.
1982-01-01
Reviewed in this statement are methods of preparing solutions to be used in laboratory experiments to examine technical issues related to the safe disposal of nuclear waste from power generation. Each approach currently used to prepare solutions has advantages and any one approach may be preferred over the others in particular situations, depending upon the goals of the experimental program. These advantages are highlighted herein for three approaches to solution preparation that are currently used most in studies of nuclear waste disposal. Discussion of the disadvantages of each approach is presented to help a user select a preparation method for his particular studies. Also presented in this statement are general observations regarding solution preparation. These observations are used as examples of the types of concerns that need to be addressed regarding solution preparation. As shown by these examples, prior to experimentation or chemical analyses, laboratory techniques based on scientific knowledge of solutions can be applied to solutions, often resulting in great improvement in the usefulness of results.
Yang, Yu; Yao, Hongwei; Hong, Mei
2015-04-16
Nonlamellar lipid membranes are frequently induced by proteins that fuse, bend, and cut membranes. Understanding the mechanism of action of these proteins requires the elucidation of the membrane morphologies that they induce. While hexagonal phases and lamellar phases are readily identified by their characteristic solid-state NMR line shapes, bicontinuous lipid cubic phases are more difficult to discern, since the static NMR spectra of cubic-phase lipids consist of an isotropic (31)P or (2)H peak, indistinguishable from the spectra of isotropic membrane morphologies such as micelles and small vesicles. To date, small-angle X-ray scattering is the only method to identify bicontinuous lipid cubic phases. To explore unique NMR signatures of lipid cubic phases, we first describe the orientation distribution of lipid molecules in cubic phases and simulate the static (31)P chemical shift line shapes of oriented cubic-phase membranes in the limit of slow lateral diffusion. We then show that (31)P T2 relaxation times differ significantly between isotropic micelles and cubic-phase membranes: the latter exhibit 2 orders of magnitude shorter T2 relaxation times. These differences are explained by the different time scales of lipid lateral diffusion on the cubic-phase surface versus the time scales of micelle tumbling. Using this relaxation NMR approach, we investigated a DOPE membrane containing the transmembrane domain (TMD) of a viral fusion protein. The static (31)P spectrum of DOPE shows an isotropic peak, whose T2 relaxation times correspond to that of a cubic phase. Thus, the viral fusion protein TMD induces negative Gaussian curvature, which is an intrinsic characteristic of cubic phases, to the DOPE membrane. This curvature induction has important implications to the mechanism of virus-cell fusion. This study establishes a simple NMR diagnostic probe of lipid cubic phases, which is expected to be useful for studying many protein-induced membrane remodeling phenomena
Energy Technology Data Exchange (ETDEWEB)
Yuan, Wenhui, E-mail: cewhyuan@scut.edu.cn [School of Chemistry and Chemical Engineering, South China University of Technology 510640, Guangdong, Guangzhou (China); Liu, Xiaoxia [School of Chemistry and Chemical Engineering, South China University of Technology 510640, Guangdong, Guangzhou (China); Li, Li [College of Environmental Science and Engineering, South China University of Technology 510006, Guangdong, Guangzhou (China)
2014-11-15
Graphical abstract: Hydrothermal synthesis method was applied for preparation of cubic-like CuCr{sub 2}O{sub 4} spinel nanoparticles without template. The synthesized cubic-like CuCr{sub 2}O{sub 4} shows excellent photocatalytic activity for degradation of RhB and MB cationic dyes but not for MO anionic dye in the presence of H{sub 2}O{sub 2} under visible light irradiation. - Highlights: • The cubic-like CuCr{sub 2}O{sub 4} spinel nanoparticles were successfully synthesized via the hydrothermal synthesis method. • The calcination temperature has a great influence on the morphology, particle size and photocatalytic activity of CuCr{sub 2}O{sub 4}. • The pH at the point of zero charge (pH{sub pzc}) of the CuCr{sub 2}O{sub 4} calcined at 600 °C is about 4.52. • The cubic-like CuCr{sub 2}O{sub 4} calcined at 600 °C exhibits excellent photocatalytic activity for RhB and MB in the presence of H{sub 2}O{sub 2} under visible-light irradiation. - Abstract: CuCr{sub 2}O{sub 4} nanoparticles with cubic-like morphology were prepared via hydrothermal synthesis method without template. The CuCr{sub 2}O{sub 4} samples were characterized by thermogravimetry and differential scanning calorimetry (TG–DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra (DRS) and Zeta potentials, respectively. The results indicated that cubic-like CuCr{sub 2}O{sub 4} could be successfully synthesized by calcining the precursor at 600 °C, and the calcination temperature greatly influenced the morphology and optical performance of CuCr{sub 2}O{sub 4}. The pH at the point of zero charge (pH{sub pzc}) of the CuCr{sub 2}O{sub 4} calcined at 600 °C was about 4.52. The photocatalytic activity of CuCr{sub 2}O{sub 4} was evaluated for degradation of rhodamine B (RhB), methylene blue (MB), and methyl orange (MO) in the presence of H{sub 2}O{sub 2} under visible light irradiation and the effects of the
Functional Ag porous films prepared by electrospinning
Dong, Guoping; Xiao, Xiudi; Liu, Xiaofeng; Qian, Bin; Liao, Yang; Wang, Chen; Chen, Danping; Qiu, Jianrong
2009-06-01
Face-centered cubic Ag porous films have been prepared directly from the heat treatment of AgNO 3-doped poly(vinyl alcohol) (PVA) electrospun nanofibers. Using Rhodamine B (RB) as the probing molecule, the surface-enhanced Raman scattering (SERS) effect of Ag porous films was demonstrated. The antibacterial activity of Ag porous films was also studied in this work. The propagation and biological activity of yeast cells were effectively inhibited by Ag porous films. These functional Ag porous films were expected to be applied in many fields, such as catalysis, diagnostics, sensors and antibacterial, etc.
Motion of a Rigid Rod Rocking Back and Forth Cubic-Quintic Duffing Oscillators
DEFF Research Database (Denmark)
Ganji, S. S.; Barari, Amin; Karimpour, S.
2012-01-01
In this work, we implemented the first-order approximation of the Iteration Perturbation Method (IPM) for approximating the behavior of a rigid rod rocking back and forth on a circular surface without slipping as well as Cubic-Quintic Duffing Oscillators. Comparing the results with the exact...
The thermal expansion of a face-centered cubic lattice with central two-body interactions
Bicknese, V.
1965-01-01
The thermal expansion e is calculated by minimizing the free energy, including the cubic and quartic phonon-interaction terms. The free energy is expanded to third order in e. The work is closely related to that of Maradudin and Maradudin, Flinn and Coldwell-Horsfall. The resulting formulas are appl
Magnetic Behaviour of the Cubic La(Fe,Al)13 Compounds
Kraan, A.M. van der; Buschow, K.H.J.; Palstra, T.T.M.
1983-01-01
The magnetic properties of the cubic NaZn13 type pseudobinary compounds LaFexAl13-x were studied in the temperature range T=4.2 - 300 K by means of 57Fe-Mössbauer spectroscopy, magnetization and zero-field susceptibility measurements. The compounds LaFexAl13-x show a rather peculiar concentration de
KOELINK, MH; DEMUL, FFM; GREVE, J; GRAAFF, R; DASSEL, ACM; AARNOUDSE, JG
1992-01-01
In addition to the static cubic lattice model for photon migration in turbid biological media by Bonner et al. [J. Opt. Soc. Am. A 4, 423-432 (1987)], a dynamic method is presented to calculate the average absolute Doppler shift as a function of the distance between the point of injection of photons
Indian Academy of Sciences (India)
R S Kaushal; Ranjit Kumar; Awadhesh Prasad
2006-08-01
Attempts have been made to look for the soliton content in the solutions of the recently studied nonlinear diffusion-reaction equations [R S Kaushal, J. Phys. 38, 3897 (2005)] involving quadratic or cubic nonlinearities in addition to the convective flux term which renders the system nonconservative and the corresponding Hamiltonian non-Hermitian.
Cubic Trigonometric B-spline Galerkin Methods for the Regularized Long Wave Equation
Irk, Dursun; Keskin, Pinar
2016-10-01
A numerical solution of the Regularized Long Wave (RLW) equation is obtained using Galerkin finite element method, based on Crank Nicolson method for the time integration and cubic trigonometric B-spline functions for the space integration. After two different linearization techniques are applied, the proposed algorithms are tested on the problems of propagation of a solitary wave and interaction of two solitary waves.
Motion of a Rigid Rod Rocking Back and Forth Cubic-Quintic Duffing Oscillators
DEFF Research Database (Denmark)
Ganji, S. S.; Barari, Amin; Karimpour, S.
2012-01-01
In this work, we implemented the first-order approximation of the Iteration Perturbation Method (IPM) for approximating the behavior of a rigid rod rocking back and forth on a circular surface without slipping as well as Cubic-Quintic Duffing Oscillators. Comparing the results with the exact...
On the 3-rank of tame kernels of certain pure cubic number fields
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
In this paper,we present some explicit formulas for the 3-rank of the tame kernels of certain pure cubic number fields,and give the density results concerning the 3-rank of the tame kernels.Numerical examples are given in Tables 1 and 2.
Phonon softening induced cubic-to-tetragonal phase transition in ReO3
Liu, Yaming; Zhang, Niu; Jia, Yu; Sun, Qiang; Chao, Mingju
2015-10-01
Within density functional theory, the structural, electronic and lattice dynamical properties of ReO3 in cubic Pm-3m and tetragonal P4/mbm phases are studied by using quasiharmonic approximation. The enthalpy-pressure curves show that a phase transition may take place at 5.0 kbar and the nonexistence of imaginary frequency in phonon dispersions demonstrates the two phases are dynamically stable under proper conditions. With the increase of pressure, an obvious softening of M3 mode at M point appears in cubic phase, and a cubic-to-tetragonal phase transition is accompanied with the presence of negative frequency in M3 mode at 5.0 kbar. In detail, one type of O atoms displaced from x = 0.2500 to x = 0.2401, which corresponds to the softening of M3 mode, are responsible for the phase transition. Our theoretical results show that ReO3 can exist in the tetragonal P4/mbm phase, and a cubic-to-tetragonal phase transition will appear at around 5.0 kbar.
The bulk modulus of cubic spinel selenides: an experimental and theoretical study
DEFF Research Database (Denmark)
Waskowska, A.; Gerward, Leif; Olsen, J.S.
2009-01-01
It is argued that mainly the selenium sublattice determines the overall compressibility of the cubic spinel selenides, AB2Se4, and that the bulk modulus for these compounds is about 100GPa. The hypothesis is supported by experiments using high-pressure X-ray diffraction and synchrotron radiation...
Recovery of Graded Index Profile of Planar Waveguide by Cubic Spline Function
Institute of Scientific and Technical Information of China (English)
YANG Yong; CHEN Xian-Feng; LIAO Wei-Jun; XIA Yu-Xing
2007-01-01
A method is proposed to recover the refractive index profile of graded waveguide from the effective indices by a cubic spline interpolation function. Numerical analysis of several typical index distributions show that the refractive index profile can be reconstructed closely to its exact profile by the presented interpolation model.
Polarized infrared reflectance study of free standing cubic GaN grown by molecular beam epitaxy
Energy Technology Data Exchange (ETDEWEB)
Lee, S.C., E-mail: saicheonglee86@yahoo.com [Nano-Optoelectronics Research Laboratory, School of Physics, Universiti Sains Malaysia, 11800 Penang (Malaysia); Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia); Ng, S.S.; Hassan, H. Abu; Hassan, Z.; Zainal, N. [Nano-Optoelectronics Research Laboratory, School of Physics, Universiti Sains Malaysia, 11800 Penang (Malaysia); Novikov, S.V.; Foxon, C.T.; Kent, A.J. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom)
2014-07-01
Optical properties of free standing cubic gallium nitride grown by molecular beam epitaxy system are investigated by a polarized infrared (IR) reflectance technique. A strong reststrahlen band, which reveals the bulk-like optical phonon frequencies, is observed. Meanwhile, continuous oscillation fringes, which indicate the sample consists of two homogeneous layers with different dielectric constants, are observed in the non-reststrahlen region. By obtaining the first derivative of polarized IR reflectance spectra measured at higher angles of incidence, extra phonon resonances are identified at the edges of the reststrahlen band. The observations are verified with the theoretical results simulated based on a multi-oscillator model. - Highlights: • First time experimental studies of IR optical phonons in bulk like, cubic GaN layer. • Detection of extra phonon modes of cubic GaN by polarized IR reflectance technique. • Revelation of IR multiphonon modes of cubic GaN by first derivative numerical method. • Observation of multiphonon modes requires very high angle of incidence. • Resonance splitting effect induced by third phonon mode is a qualitative indicator.
Directory of Open Access Journals (Sweden)
K. Ravi
2014-03-01
Full Text Available In this paper, using fixed point method we prove the generalized Hyers Ulam Rassias stability of the additive cubic functional equationf(x-ky=k2[f(x+y+ f(x-y]+2(1- k2f(x for fixed integers k, with k≠0,±1 in paranormed spaces.
Hilhorst, J.; Wolters, J. R.; Petukhov, A.V.
2010-01-01
Hard sphere crystal growth is a delicate interplay between kinetics and thermodynamics, where the former is commonly thought to favour a random hexagonal close packed structure and the latter leads to a face centered cubic crystal. In this article, we discuss the influence of slanted stacking faults
New Optical Solitons in High-Order Dispersive Cubic-Quintic Nonlinear Schrodinger Equation
Institute of Scientific and Technical Information of China (English)
LI Hua-Mei; XU You-Shen; LIN Ji
2004-01-01
By using the generalized tanh-function method, we find bright and dark solitary wave solutions to an extended nonlinear Schrodinger equation with the third-order and fourth-order dispersion and the cubic-quintic nonlinear terms, describing the propagation of extremely short pulses. At the same time, we also obtained other types of exact solutions.
Cross-polarized wave generation by effective cubic nonlinear optical interaction.
Petrov, G I; Albert, O; Etchepare, J; Saltiel, S M
2001-03-15
A new cubic nonlinear optical effect in which a linearly polarized wave propagating in a single quadratic medium is converted into a wave that is cross polarized to the input wave is observed in BBO crystal. The effect is explained by cascading of two different second-order processes: second-harmonic generation and difference frequency mixing.
Lee, Hyunjoo; Habas, Susan E; Somorjai, Gabor A; Yang, Peidong
2008-04-23
Binary Pt/Pd nanoparticles were synthesized by localized overgrowth of Pd on cubic Pt seeds for the investigation of electrocatalytic formic acid oxidation. The binary particles exhibited much less self-poisoning and a lower activation energy relative to Pt nanocubes, consistent with the single crystal study.
Rakhimov, Abdulla; Askerzade, Iman N
2014-09-01
We have shown that the critical temperature of a Bose-Einstein condensate to a normal phase transition of noninteracting bosons in cubic optical lattices has a linear dependence on the filling factor, especially at large densities. The condensed fraction exhibits a linear power law dependence on temperature in contrast to the case of ideal homogeneous Bose gases.
HOSHI, Akinari; Miyake, Katsuya
2007-01-01
We study the field isomorphism problem for a cubic generic polynomial $X^3+sX+s$ via Tschirnhausen transformation. Through this process, there naturally appears a $2$-dimensional involutive Cremona transformation. We show that the fixed field under the action of the transformation is purely transcendental over an arbitrary base field.
A sub-cubic time algorithm for computing the quartet distance between two general trees
DEFF Research Database (Denmark)
Nielsen, Jesper; Kristensen, Anders Kabell; Mailund, Thomas;
2011-01-01
derived a new algorithm for computing the quartet distance between a pair of general trees, i.e. trees where inner nodes can have any degree ≥ 3. The time and space complexity of our algorithm is sub-cubic in the number of leaves and does not depend on the degree of the inner nodes. This makes...